SB 


,«jor4  w.  PIS 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


;  - 


THE 
Wireless   Operators'    Pocketbook 

OF 

INFORMATION  AND  DIAGRAMS 


BY 

LEON  W.  BISHOP 

\   9 


1911 
BUBIER  PUBLISHING  COMPANY 

LYNN,  MASS.,  U.  S.  A. 

AND 

H.  ALABASTER  GATEHOUSE  CO. 
LONDON,  ENG. 


COPYRIGHTED  1911 

BY 

BUSIER  PUBLISHING  COMPANY 
LYNN,  MASS. 

ENTERED  AT  STATIONERS'  HALL 
LONDON,  ENGLAND 

BY 

H.  ALABASTER  GATEHOUSE  Co. 
1911 


THE   PLIMPTON   PRESS   NORWOOD   MASS,  U.S.A. 


PREFACE 

THE  purpose  of  this  little  manual  is  to  satisfy  the 
desires  of  the  wireless  operator  and  of  those  experi- 
menters who  have  already  some  knowledge  of  wire- 
less phenomena,  and  who  wish  for  a  practical  book 
more  suited  to  their  needs  than  the  many  elementary 
ones  which  deal  mostly  with  the  construction  of  simple 
apparatus,  or  the  elaborate  technical  and  mathematical 
treatises  which  presuppose  a  technical  education  to 
understand  them.  Although  some  acquaintance  with 
wireless  apparatus  is  expected,  it  has  been  the  author's 
intention  to  give  enough  of  the  theory  of  the  circuits 
and  of  each  piece  of  apparatus  so  that  anyone  inter- 
ested may  understand  it  and  its  working. 

So  far  as  is  possible  it  has  been  intended  to  take  up 
the  various  subjects  in  their  logical  order,  except 
perhaps  where  a  purely  logical  order  would  not  at  the 
same  time  aid  in  the  general  clearness  of  explanation. 
The  treatment  of  the  transmitting  and  receiving  instru- 
ments, the  ground  and  the  aerial  connections,  naturally 
comes  before  the  more  general  chapters.  The  chapters 
descriptive  of  instruments  are  also  noticeably  more 
simple  than  those  towards  the  end  of  the  book,  where 
a  further  familiarity  with  the  author's  expression  is 

222658 


vi  PREFACE 

expected.  Moreover,  it  is  to  be  noticed  that  although 
most  of  the  popular  forms  of  instruments  are  mentioned 
and  described,  some  have  been  omitted.  This  has 
usually  been  intentional,  in  order  to  comprise  within 
the  smallest  possible  space  the  description  of  late 
types  of  apparatus,  and  that  of  the  most  approved 
and  efficient  design. 

The  author's  knowledge  of  wireless  is  based  largely 
on  his  experience  in  the  Stone  Company,  and  under 
the  direction  of  Mr.  John  Stone  Stone.  He  is  also 
largely  indebted  to  Mr.  G.  W.  Pickard  for  information 
during  the  writing  of  this  book.  Both  Mr.  Stone 
and  Mr.  Pickard  have  freely  allowed  the  reproduction 
of  their  circuits  and  theories.  On  telephony,  he  is 
also  indebted  to  Mr.  Lee  DeForest  and  others. 
Thanks  are  by  this  means  extended  to  those  whose 
names  are  mentioned  and  to  many  others  for  help  re- 
ceived, either  personally  or  from  their  printed  works. 


CONTENTS 

PAGE 

I    THE  TRANSMITTING  CIRCUIT i 

II     TRANSMITTING  STATIONS:  EXPERIMENTAL  OR  LOW- 
POWER  APPARATUS 10 

III  TRANSMITTING     APPARATUS:     PROFESSIONAL     OR 

HIGH-POWER  STATIONS 17 

IV  THE  RECEIVING  CIRCUIT 32 

V     RECEIVING  APPARATUS        40 

VI    AERIALS  AND  GROUNDS:  TYPES  AND  CONSTRUCTION  68 

VII    PROTECTION  AND  INSTALLATION  or  A  STATION       .  80 

VIII    OPERATION  OF  A  STATION        go 

IX     BREAKING-IN    SYSTEMS:    METHODS    OF     SIMULTA- 
NEOUS RECEIVING  AND  TRANSMITTING      .     .     .  107 

X     CODES 121 

XI     THE  ETIQUETTE  OF  WIRELESS  AND  THE    SUBJECT 

OF  INTERFERENCE 129 

XII     WIRELESS  TELEPHONY 133 

APPENDIX 149 

SUPPLEMENT.    LATEST  CALL  LETTERS    . 


vii 


WIRELESS  OPERATORS' 
POCKETBOOK 

CHAPTER  I 

THE    TRANSMITTING   CIRCUIT 

WIRELESS  communication  is  accomplished  by  means 
of  vibrations  set  up  in  the  ether  by  a  set  of  special 
instruments  used  for  creating  and  transmitting  them. 
These  vibrations,  which  travel  in  all  directions  away 
from  the  sending  station  in  the  form  of  waves,  are 
created  of  a  certain  length  and  frequency  by  the 
action  of  a  number  of  different  instruments,  each  of 
which  affects  the  wave-creating  current  in  a  definite 
manner.  If,  for  instance,  we  take  the  following  sche- 
matic diagram  of  the  transmitting  apparatus,  we  may 
understand  the  part  played  by  each  instrument  toward 
the  desired  result  of  producing  intelligible  effect  upon 
telephone  receivers  at  any  station. 

An  electric  current,  set  up  by  the  batteries  of  the 
primary  circuit,  passes  through  the  primary  winding 
of  the  spark  coil.  This  would  form  a  closed  circuit, 
except  for  the  fact  that  a  telegraph  key,  connected 
between  batteries  and  primary,  allows  the  operator 
to  make  and  break  the  flow  of  current  at  his  own  will. 
When  the  key  is  held  down  for  an  instant  only,  the 

1 


WIRELESS  OPERATORS'   POCKETBOOK 


current  flowing  through  the  circuit  makes  a  '  elegraphic 
"dot."  If  held  down  for  a  longer  period,  we  have  a 
telegraphic  "dash."  It  is  thus  the  will  of  the  operator 
which  controls  the  flow  of  current  through  this  primary 
circuit,  transferring  his  thoughts,  by  means  of  an 
established  code,  to  the  receiving  station. 


UJ 


F  I    G.I. 

The  current  of  our  primary  circuit  is  direct.  There 
must,  however,  be  alternating  current  for  the  secondary. 
Therefore  some  form  of  interrupter  must  be  placed 
in  the  primary  circuit  in  order  to  break  the  current 
and  to  give  it  the  necessary  pulsations.  A  mechanical 
vibrator  connected  to  the  primary  of  the  spark  coil  is 
most  frequently  used,  although  an  electrical  inter- 
rupter on  a  separate  battery  circuit  may  be  employed 
instead. 


THE  TRANSMITTING  CIRCUIT  3 

This  Vibrator  interrupts  the  steady  current  in  the 
primary  of  the  spark  coil,  varying  the  magnetism  of 
the  core,  by  constantly  changing  its  polarity.  The 
secondary  of  the  coil  picks  up  the  magnetism;  and 
because  the  number  of  turns  of  wire  on  a  secondary 
are  proportionately  greater  than  on  a  primary,  the 


F  I  D, 


secondary  transforms  this  magnetism  into  a  current 
of  higher  voltage.  Whereas  we  had  in  the  primary 
circuit  a  direct  current  of  low  voltage,  we  have  now  in 
the  secondary  an  alternating  current  of  high  voltage. 

The  current  rushes  into  the  aerial,  filling  or  charging 
it,  and  this  charge  creates  an  electro-static  field  around 
it.  Now,  if  the  current  ceases  to  flow,  the  lines  of 
force  of  this  field  will  fall  flat.  We  then  place  a  spark 


WIRELESS  OPERATORS'  POCKETBOOK 


FI  &. 


THE   TRANSMITTING  CIRCUIT 


gap  between  aerial  and  ground.  Now,  when  the  aerial 
charge  is  great  enough  to  overcome  the  resistance  of 
air  between  the  points  of  the  spark  gap,  a  spark 
will  jump  between  them,  thus  discharging  the  aerial 
abruptly  and  jerking  the  lines  of  force  sharply  to  the 
ground.  The  repeated  charge  of  the  aerial  and  its 


LU 


FI&. 


repeated  discharge  through  the  spark  gap  will  snap 
off  portions  of  the  field,  detach  them  from  the  aerial, 
and  thus  form  electric  waves.  Series  or  trains  of 
these  detached  waves  follow  one  another  with  great 
velocity,  travelling  at  the  same  speed  as  light  (186,400 
miles  per  second). 
Instruments  connected  according  to  Figs.  3  and  4 


WIRELESS  OPERATORS1  POCKETBOOK 


will  transmit  messages  into  space,  but  our  wave 
frequency  will  be  very  high,  and  therefore  the  wave 
length  will  be  very  short.  Now  short  waves  are  espe- 
cially liable  to  all  influences  tending  to  shorten  their 
lives  —  to  absorption  by  the  neighboring  hills  and  trees, 
to  reflection  and  refraction,  which  tend  to  change  their 
direction,  and  to  polarization  or  complete  annihilation. 


LU 


FI&. 


Therefore  short  waves  are  inefficient  for  transmission 
to  any  distance.  In  order  to  lengthen  the  waves,  we 
must  decrease  their  frequency.  If  a  coil  is  placed  in 
the  aerial  (between  spark  gap  and  aerial)  it  will  pro- 
duce this  effect,  and  the  waves  will  be  lengthened. 
A  condenser  across  the  spark  gap  will  produce  a 
similar  effect  in  lengthening  the  waves.  By  combin- 
ing the  two,  using  both  coil  and  condenser,  we  will 
add  together  the  two  effects.  Not  only  can  we  obtain 


THE  TRANSMITTING  CIRCUIT  7 

the  desired  long  waves  in  the  manner  shown  in  Fig.  7, 
but  coil  and  condenser  may  be  placed  in  series  (see 
Fig.  i),  with  the  same  results;  or  they  may  be  con- 
nected as  shown  uf  Fig.  8.  Usually  it  is  considered 
best  to  have  both  devices  together.  Thus  is  formed 
a  resonance  or  oscillatory  circuit,  in  which  the  amount 


FIG. 7 


of  inductance  and  capacity  (i.e.  of  coil  and  condenser) 
offers  a  path  for  a  spark  discharge  of  a  certain  perio- 
dicity; that  is,  of  a  definite  wave  length  and  frequency. 
It  is  to  be  noted  that  under  normal  conditions  the 
aerial  acts  as  a  condenser,  aerial  being  one  plate  and 
ground  the  other. 

Thus  are  formed  the  simplest  forms  of  transmit- 
ting circuits.      An  oscillation  transformer  will  give  us 


. 


8j  WIRELESS  OPERATORS'   POCKET  BOOK 

an  additional  circuit,  which  with  coil  and  condenser 
balanced  with  the  first  circuit  will  again  be  in  reso- 
nance. By  substituting  an  oscillation  transformer  for 
a  helix,  we  do  not  really  change  the  circuit  formerly 
used,  we  merely  separate  the  primary  entirely  from 
the  secondary,  while  both  of  them  existed  on  the  helix. 


By  separating  them  completely  we  gain  an  additional 
variation,  that  of  the  distance  between  the  two  coils, 
the  coupling.  If  these  coils  are  drawn  far  apart,  the 
tuning  is  made  very  sharp,  the  signals  can  only  be 
received  when  the  oscillation  transformer  used  in  the 
receiving  station  has  a  carefully  ascertained  amount 
of  primary,  secondary,  and  coupling.  Such  an  arrange- 
ment of  the  oscillation  transformer  at  the  sending 
station  would  be  ideal,  if  it  were  not  for  the  fact  that 


THE  TRANSMITTING  CIRCUIT  Q 

more  energy  is  lost  when  the  coils  are  at  a  great  distance 
apart,  and  consequently  the  transmitting  distance  of 
the  station  is  lessened.  However,  if'  the  coils  are  too 
near  together,  there  will  be  another  set  of  waves  formed, 
following  the  first,  but  with  crests  between.  This  sec- 
ond tuning  point  will  detract  from  the  strength  of 
signals  at  the  first  point,  and  as  a  consequence  the 
receiving  station  will  get  its  signals  less  clearly. 


CHAPTER  II 

TRANSMITTING    STATIONS:    EXPERIMENTAL    OR    LOW- 
POWER  APPARATUS 

THE  experimenter's  station  will  usually  consist  of 
the  following  pieces  of  apparatus  for  transmitting: 

Batteries  Spark  Gap 

Telegraph  Key  Condenser 

Spark  Coil  Helix 

'Lhe  Primary  Circuit.  Batteries  are  the  most  avail- 
able source  of  power  unless  the  electric  light  current 
is  already  installed  in  the  house.  For  low-power 
apparatus,  the  dry  battery  is  most  commonly  used, 
is  fairly  cheap,  and  requires  little  or  no  care.  The 
Storage  or  Edison-Lalande  cells  are  more  efficient, 
and  cheaper  in  the  long  run,  even  if  somewhat  more 
trouble  to  handle  and  keep  in  order.  The  advantage 
of  any  one  of  these  over  the  ordinary  wet  batteries  is 
that  the  amperage  is  higher,  and  high  amperage  is 
necessary  to  operate  a  spark  coil. 

In  selecting  dry  batteries,  the  best  one  for  wireless 
work  will  have  only  a  moderate  amount  of  amperage, 
however;  say,  18  to  22;  and  not  a  high  amperage  of 

10 


TRANSMITTING  STATIONS  11 

from  30  to  35,  as  the  latter  deteriorates  much  more 
rapidly.  In  order  to  get  the  best  and  most  lasting 
results,  the  cells  should  be  connected  in  series  multiple. 
Thus  the  amperage  of  the  number  in  multiple  is  larger 
and  the  voltage  is  less  than  when  connected  in  series. 
Only  a  storage  cell  of  a  known  make  should  be  used, 
as  a  poor  one  will  prove  very  expensive  to  maintain. 
The  storage  battery  has  the  decided  advantage  over 
the  dry  battery  that  its  output  is  always  even. 

Telegraph  Keys  in  regular  use  by  commercial  com- 
panies are  adapted  for  wireless  work.  Either  the  leg 
or  the  legless  type  is  well  suited  to  all  requirements. 
Platinum  contact  points  are  essential  and  are  usually 
found  on  commercial  types  of  keys.  For  the  rest, 
easy  action  and  capability  of  fine  adjustment  are  all 
that  need  be  looked  for  in  buying  one. 

The  Spark  Coil  increases  (or  technically  speaking, 
"steps  up")  the  voltage  in  order  to  charge  the  aerial, 
and  thus  to  create  around  it  an  electro-static  field 
which  is  to  be  broken  down  by  the  spark  gap.  A 
good  coil  is  more  cheaply  bought  than  made,  except 
in  the  larger  sizes.  Such  a  coil,  to  be  thoroughly 
reliable,  must  be  carefully  constructed;  and  it  is  diffi- 
cult for  the  experimenter  to  use  all  the  precautions 
necessary  to  avoid  loss  of  energy.  A  coil  of  good 
efficiency  is  built  with  a  primary  of  two  layers  of  nos. 
14  to  1 8  single  covered  copper  wire,  wound  on  a  core 
of  soft  drawn  iron  wires.  The  secondary  is  wound 
with  a  very  fine  wire,  nos.  34  to  38,  and  carefully 


12         WIRELESS  OPERATORS'   POCKETBOOK 

insulated.  Enamelled  wire  in  coils,  as  on  most  pieces 
of  wireless  apparatus,  is  not  satisfactory;  the  weather 
is  apt  to  affect  the  enamel,  crack  it,  and  thus  spoil  its 
insulating  qualities. 

Coils  are  classified  by  the  manufacturer  according 
to  the  distance  the  spark  will  jump.  This  jump  spark 
is  long  and  thin,  and  is  unsuited  for  wireless  work. 
For  this  purpose,  a  short  thick  spark,  demanding 
a  relatively  high  amperage  is  necessary,  the  same 
names  are  applied,  however  contrary  they  may  seem 
to  the  facts  of  the  case.  Thus,  a  one-inch  coil,  suitable 
for  wireless,  should  give  a  one-half  inch  spark,  suffi- 
ciently thick  and  hot  to  ignite  a  piece  of  paper  placed 
between  the  sparking  points.  This  short  thick  spark 
is  called  the  " caterpillar  spark."  In  buying  a  coil, 
a  good  test  is  to  draw  out  the  spark  to  the  breaking 
point.  If  good,  the  discharges  should  then  sound  very 
sharply.  This  loudness  of  discharge,  together  with  the 
hot  caterpillar  spark,  shows  the  coil  adapted  for  wire- 
less work. 

The  Vibrator  interrupts  a  current  in  the  primary 
of  the  spark  coil,  thus  producing  magnetism  on  the 
core,  which  is  picked  up  by  the  secondary.  To  give 
satisfactory  results,  a  coil  must  have  a  good  vibrator. 
Such  a  vibrator  should  have  either  platinum  or  iridium 
contacts,  and  the  larger  the  better.  The  vibrator 
giving  a  high-pitched  spark  is  much  better  than  a 
vibrator  giving  one  of  low  pitch.  Not  only  does  it 
give  more  current  to  the  primary,  but  it  causes 


TRANSMITTING  STATIONS  13 

a  spark  which  is  more  penetrating,  is  more  easily  read, 
and  at  a  greater  distance.  Such  a  vibrator  is  by  all 
means  the  one  to  choose,  even  although  it  consumes 
the  battery  current  somewhat  more  rapidly  than  one 
of  lower  pitch. 

All  commercial  spark  coils  are  fitted  with  a  condenser 
across  the  vibrator  to  stop  the  sparking  at  the  vibra- 
tor contacts.  By  this  means  the  current  is  abruptly 
broken,  and  thus  the  interruptions  are  sharper.  Such 
a  condenser  is  very  essential,  and  must  be  carefully 


F  I  G.7 

fitted  in  capacity  to  the  vibrator  by  an  expert.     It  is 
not  well  to  tamper  with  it  or  to  change  its  value. 

The  Spark  Gap  discharges  the  charged  aerial,  and  thus 
creates  a  series  or  train  of  electro-magnetic  waves. 
The  electrodes  of  a  good  spark  gap  are  of  the  utmost 
importance,  both  as  to  their  form  and  as  to  the  material 
of  which  they  are  made.  The  best  form  for  the 
electrodes  is  that  of  a  flat-faced  circular  rod.  A  sharply 
pointed  or  spherical  electrode  wastes  energy  and  is 
less  desirable.  As  to  materials,  silver  is  best  of  all, 
because  while  it  is  an  excellent  conductor  when  new, 
the  oxide  forming  when  it  becomes  black  is  almost  as 
good  a  conductor  as  the  pure  silver.  Moreover,  silver 


14   WIRELESS  OPERATORS'  POCKETBOOK 

is  less  apt  to  allow  an  arc  to  form  across  the  gap. 
Pure  tin  also  forms  a  good  electrode.  For  general 
use,  a  commercial  compound  known  as  nickel-steel 
may  be  recommended.  There  is  no  difference  between 
the  horizontal  and  the  vertical  types  in  efficiency, 
although  one  should  always  choose  the  Gap  with  the 
finest  adjustments. 

The  Condenser  is  a  unit  of  balance  in  the  transmitting 
set.  The  aerial,  helix,  and  condenser  must  all  be 
brought  into  resonance  in  order  to  transmit  the  waves 
to  greater  distances.  This  rinding  a  point  of  resonance 
is  the  important  thing.  Almost  always  the  condenser 
is  of  a  fixed  value,  although  it  is  possible  to  have  it 
variable  instead  of  the  helix,  as  is  usual.  Transmitting 
condensers  consist  generally  of  glass  plates  and  tin- 
foil. The  glass  margin  around  the  tinfoil  should  be 
wide  enough  to  prevent  sparking  over  the  edges.  The 
capacity  of  the  condenser  should  be  sufficiently  large 
to  balance  with  the  rest  of  the  circuit.  Leyden  jars 
are  also  used  as  transmitting  condensers,  although 
some  energy  may  be  lost  in  this  type  by  a  brush  dis- 
charge around  the  upper  edges  of  the  jar. 

The  Helix  is  another  unit  of  balance  in  the  set.  As 
already  stated,  it  is  oftenest  the  helix  which  is  varied 
when  bringing  the  helix,  condenser,  and  aerial  into 
resonance.  A  helix  of  soft-drawn  strip  copper  on  hard 
rubber  posts  is  the  best  one;  but  if  built  of  copper 
tubing  or  heavy  wire  (the  soft-drawn  is  always  best), 
and  on  insulated  wooden  posts,  it  will  be  satisfactory 


TRANSMITTING  STATIONS  15 

for  low-power  stations.  Helices  for  this  work  should 
have  one  stationary  and  two  variable  contacts. 

Having  completed  the  general  description  of  the 
qualities  of  the  instruments  in  a  transmitting  set,  it 
will  be  advisable  to  show  a  selection  of  instruments 
which  will  work  harmoniously  together.  The  first 
transmitting  set  usually  depends  upon  a  one-inch 
spark  coil,  and  so  that  will  be  our  starting  point. 

Transmitting  Set  No.  i.  With  a  one-inch  spark  coil, 
provided  with  a  good  high-pitched  vibrator,  there  will 
be  necessary  from  six  to  twelve  dry  cells.  Six  cells 
will  run  the  coil,  but  of  course  the  energy  will  be 
greater  with  more.  A  greater  number  than  twelve, 
however,  should  not  be  used,  as  it  may  break  down 
the  secondary  winding  and  burn  out  the  primary.  An 
ordinary  telegraph  key,  such  as  can  be  purchased  for 
about  a  dollar,  will  give  good  satisfaction.  A  spark 
gap  with  silver  points  may  be  mounted  on  the  coil  or 
on  a  separate  base.  The  transmitting  condenser  should 
consist  of  from  ten  to  fifteen  5  by  7  glass  plates  and  a 
suitable  amount  of  tinfoil  or  leadfoil,  with  good  margins. 
A  simple  home-made  helix,  made  either  of  strip  copper 
or  copper  wire,  wound  in  a  spiral  or  on  a  drum,  will  be 
all  that  is  necessary.  With  an  aerial  of  fair  size  and 
a  good  ground  connection,  this  set  of  apparatus  will 
transmit  signals  to  a  distance  of  from  four  to  seven 
miles  over  land,  or  a  somewhat  greater  distance  over 
water. 

Transmitting  Set  No.   2.     A   two-inch   spark   coil, 


16        WIRELESS   OPERATORS'   POCKETBOOK 

with  a  good  vibrator,  should  give  a  hot  caterpillar 
spark  which  will  ignite  a  piece  of  paper  when  the 
sparking  points  are  from  one  inch  to  an  inch  and  a 
quarter  apart.  Such  a  coil  requires  from  ten  to  twenty- 
four  dry  cells,  or  a  storage  battery  of  ten  to  fifteen 
volts,  sixty  ampere  hours.  The  same  key  used  for  the 
one-inch  coil  will  be  adequate  for  this  set  also.  An 
adjustable  spark  gap,  mounted  on  a  separate  base, 
would  be  best.  The  transmitting  condenser  and  the 
helix  may  be  the  same  as  those  described  for  Set  No.  i. 
Greater  pains  must  be  taken  with  the  insulation 
when  a  higher  voltage  is  used.  Such  a  set  as  this 
will  send  from  ten  to  eighteen  miles  over  land,  or  three 
times  this  distance  over  water. 

After  outgrowing  these  outfits,  the  experimenter 
will  naturally  wish  to  have  a  more  powerful  set,  and 
for  this  purpose  he  will  probably  want  a  small  trans- 
former. Sets  of  that  type  are  described  in  the  follow- 
ing section. 


CHAPTER  III 

TRANSMITTING     APPARATUS!     PROFESSIONAL     OR     HIGH- 
POWER   STATIONS 

IN  large  stations  where  high  power  is  used,  the 
apparatus  differs  from  that  used  in  smaller  ones  less 
in  character  than  in  size  and  capability  of  standing 
increased  current.  A  station  containing  a  transformer 
of  from  one-quarter  to  five  kilowatt  capacity  will  use 
the  following  apparatus: 

Alternating  Current  (or  Pulsating  Direct) 

Telegraph  Key 

Transformer 

Spark  Gap 

Condenser 

Helix,  or  better,  an  Oscillation  Transformer 

The  Power  is  usually  an  electric  light  current  of 
either  no  or  220  volts,  and  preferably  alternating. 
The  alternating  current  is  necessary  for  running  a 
transformer  to  its  best  advantage.  If  only  direct 
current,  however,  can  be  obtained,  a  somewhat  simi- 
lar effect  may  be  produced  by  using  a  chemical  or 
mechanical  interrupter  with  the  direct  current, 

17 


18        WIRELESS  OPERATORS'   POCKETBOOK 

The  Electrolytic  and  the  Mechanical  Interrupter 
produce  the  same  effect  upon  the  direct  current  and 
give  an  effect  approximating  the  alternations  of  the 
alternating  current,  which  is  what  we  need.  An 


P   I  G .   10 
A  LTE1R  N  AT  I  N  & 


C  URRE.N  f 


alternating  current  (see  Fig.  10)  makes  complete 
cycles,  passing  from  negative  to  positive,  back  again 
to  negative,  and  then  beginning  a  second  revolution. 
The  changes  of  polarity  of  this  alternating  current 
may  be  represented  by  the  curve  shown  in  Fig.  10,  a 


F  I  D  .  U 

PULSATING      c 


E.NT 


complete  cycle  being  included  between  (A)  and  (B). 
A  pulsating  direct  current,  produced  by  means  of  an 
interrupter  vibrates  between  the  zero  point  and  either 
negative  or  positive  pole,  but  it  does  not  change  its 


TRANSMITTING  APPARATUS 


19 


direction  or  polarity.  Such  a  current  may  be  repre- 
sented by  the  curve  shown  in  Fig.  n.  There  are  thus 
no  cycles,  but  the  vibrations  or  pulsations  have  much 
the  same  effect  upon  a  transformer  as  the  alternations 
of  the  alternating  current.  An  Electrolytic  or  Chemi- 
cal Interrupter  produces  pulsations  of  the  direct  current 
in  this  manner:  The  positive  lead  goes  to  the  anode 
in  a  glass  jar  containing  a  mixture  of  approximately 


PI  G.J2 

nine  parts  water  to  one  of  sulphuric  acid.  When  a 
current  passes  through  this,  bubbles  are  formed  at 
the  anode,  and  these  discharging,  the  current  from  the 
large  kathode  or  negative  plate  rushes  to  fill  up  the 
space  and  thus  completes  the  circuit.  This  is  done 
at  very  rapid  intervals.  A  battery  current  of  fifty 
volts  is  necessary  to  start  the  operation. 

Mechanical  Interrupters  are  of  many  types,  but  of 
nearly  the  same  effectiveness.  It  is  much  better  to 
buy  a  good  instrument  than  to  attempt  to  make  one. 


20         WIRELESS  OPERATORS'   POCKETBOOK 


It  should  be  of  high  pitch,  and  as  simple  in  construc- 
tion as  possible.  An  excellent  interrupter  is  shown  in 
the  diagram,  Fig.  13.  Its  principle  is  that  of  the 
electric  buzzer.  It  consists  of  a  vibrating  steel  spring 
suspended  tightly  between  two  points.  On  one  side 
of  the  spring  is  a  magnet,  and  just  above  is  a  heavy 
platinum  contact.  The  current,  passing  through  the 
magnet,  pulls  down  the  spring  and  thus  breaks  the 


F  I  Gr.   13 
AXLCHANICAL        INTERRUPTER 

circuit.  At  once  the  spring  jumps  back  again  to 
the  contact  and  starts  the  current  again.  These 
interruptions  are  .at  a  very  rapid  rate  and  at  a  high 
pitch,  which  may  be  varied  by  adjusting  the  spring. 
The  pitch  will  also  give  a  pure  tone,  such  as  is  easily 
read  at  the  receiving  end. 

The  Key  may  be  any  one  of  the  more  substantial 
makes  of  commercial  telegraph  keys,  provided  there 
are  heavy  platinum  contacts.  Special  wireless  keys 


TRANSMITTING  APPARATUS 


21 


suitable  for  use  with  transformers  of  from  J  to  2  kilo- 
watts are  manufactured,  and  there  are  larger  ones  for 
heavier  currents.  The  contacts  may  be  of  platinum, 
iridium,  or  silver,  a  compound  of  platinum  and  iridium 
making  the  best  ones.  A  key  for  use  with  a  J  to  2 
kw.  transformer  should  have  contacts  of  about  no.  10 
wire.  All  keys  used  in  high-power  stations  should 
have  a  one  microfarad  condenser  strapped  (or  shunted) 


i 


1 

1 

FIG  .17- 
OPEN      CORE       THANSFO 


across  the  contact  points  to  prevent  an  arc  from  form- 
ing or  the  key  from  sticking. 

The  Transformer,  like  the  spark  coil,  steps  up  the 
voltage  of  the  current  in  order  to  charge  the  aerial. 
Indeed  the  spark  coil  is  one  form  of  a  transformer, 
the  so-called  "open-core"  type.  In  transmitting, 
both  the  open  and  closed  core  types  may  be  used,  but 
it  is  impossible  to  use  the  latter  with  pulsating 
direct  current.  The  open-core  type  is  preferable  up  to 
5  kw.  The  closed-core  type  is  less  efficient,  although 


22   WIRELESS  OPERATORS'  POCKETBOOK 

many  prefer  it  even  in  the  smaller  sizes.  It  has  the 
advantage  that  its  size  and  output  may  be  more  closely 
computed.  The  difference  between  the  two  types 


CLOSED     COttE.     TBANSFORfAEK 
Fl  G-. 


may  be  understood  from  the  accompanying  diagrams. 
Manufacturers  have  divided  the  closed-core  types  into 
the  O  type  and  the  E  type  according  to  the  shape  of 
the  core.  The  E  type  is  perhaps  slightly  the  more 


F  I 

CLOSED      COKE     TRANSFORMER 
TYPE.     E. 

efficient,  but  both  are  good;  and  they  are  less  expen- 
sive than  the  open  or  induction  coil  type. 

The  transformer  for  wireless  work  should  have  a 
secondary  potential  of  from   15,000  to  30,000  volts. 


TRANSMITTING  APPARATUS 


23 


The  core  of  the  closed-core  transformer  should  be  built 
of  soft  iron  (laminations),  matched  together  closely. 
Insulation  should  consist  either  of  empire  cloth  or 
paper  (the  difference  is  slight)  which  is  treated  with 
a  preparation  containing  linseed  oil.  Transformers 
are  wound  both  for  no  and  220  volts,  60  or  120  cycles 


-o 


F  I  &.17 
REACTANCE          RE&ULATOR 

per  second.  Some  commercial  forms  are  so  built  that 
no  impedence  coil  or  rheostat,  such  as  is  usual,  is 
necessary. 

An  impedence  coil  and  a  rheostat  answer  the  same 
purpose  in  cutting  down  the  primary  current  of  the 
transformer,  but  in  different  ways.  An  impedence 
coil  (usually  called  a  Reactance  Regulator)  may  be 
used  only  to  cut  down  an  alternating  current.  Fig. 
17  will  show  this.  A  core  of  soft  iron  wire  has  wound 
on  it  several  layers  of  single  covered  copper  wire.  An 
alternating  current,  passing  through  the  coil,  mag- 


24   WIRELESS  OPERATORS'  POCKETBOOK 

netizes  the  core.  When  the  current  is  flowing  in  one 
direction,  the  poles  of  the  core  become  north  and  south, 
respectively.  The  change  of  direction  of  the  current 
then  reverses  this  polarity  and  tends  to  retard  the 
flow  by  bucking  it.  This  lagging  or  bucking  offers  a 
resistance  or  impedence  to  the  current.  If,  then,  this 
coil  is  tapped  at  intervals,  and  the  leads  are  connected 


F  »   D  .  18 
KHELOSTAT 

to  a  many-pointed  switch,  we  may  regulate  the  amount 
of  reactance  effect  upon  the  current. 

The  principle  of  the  rheostat  is  simpler.  A  wire  of 
lower  conductivity  is  placed  in  the  circuit  with  points 
of  adjustment,  which  determine  the  amount  of  resist- 
ance to  be  added  to  the  circuit.  This  resistance  wire 
is  often  German  silver  or  iron. 

A  bank  of  lamps  placed  in  the  circuit  has  the  same 


TRANSMITTING  APPARATUS  25 

effect,  and  because  much  cheaper,  is  often  used  for 
the  purpose.  (See  below,  Fig.  53.) 

The  Spark  Gap  in  high-power  stations  is  different 
from  that  used  in  the  smaller  stations  only  in  having 
larger  sparking  contacts,  in  its  capability  of  standing 
increased  current,  and  in  its  fineness  of  adjustment. 
Nickel-steel  is  generally  used  for  the  points,  although 
silver  is  much  better.  When  using  over  \  kw.,  radi- 
ators on  the  handles  of  the  sparking  points  will  be 
found  advantageous,  and  in  fact  almost  necessary  in 
order  to  keep  the  hot  contacts  cool,  and  thus  to  prevent 
the  formation  of  an  arc  between  them.  A  highly 
insulated  base  and  handles  are  necessary  to  prevent 
damage  to  the  operator  from  leakage  of  the  current. 
With  very  high-power  sets,  several  sparking  points 
should  be  placed  on  the  gap.  This  is  the  Multiple 
Spark  Gap.  In  connection  with  it,  a  blow-pipe  or 
fan  is  necessary  to  dissipate  the  gases  formed  and  to 
cool  the  contact  points,  since  if  hot,  these  will  allow 
the  formation  of  an  arc  between  the  gaps.  In  sets  of 
2  kw.  or  more,  the  spark  gaps  should  be  encased  in  a 
box  to  prevent  damage  to  the  operator's  eyes  from  the 
ultra-violet  rays,  and  to  his  ears  from  the  deafening 
noise.  A  glass  front  on  the  box  may  be  used,  since 
glass  is  impervious  to  the  ultra-violet  rays. 

The  Condenser,  in  high-power  sets,  should  embody 
the  same  principles  as  that  previously  described.  A 
glass-plate  condenser  is  advisable  by  all  means.  Good 
flawless  glass  should  be  used.  Plates  should  be  of  the 


26   WIRELESS  OPERATORS'  POCKETBOOK 


left  and  right  design,  since  this  ensures  an  even  capacity 
per  plate;  for  there  are  two  sheets  of  tinfoil  between 
each  one.  The  plates  should  be  arranged  in  units  so 
that  faulty  ones  may  be  removed  without  destroying 
the  whole  condenser.  It  is  well  to  have  the  plates 
cast  in  some  insulating  material  such  as  beeswax  or 
rosin;  or  to  immerse  them  in  castor  oil,  which  is  one 


n 


FIG-  19 


R  I  OH  T 
CONIDEN  5  ELPl 


LE.FT 
PL  ATE.  S 


of  the  best  dielectrics  known.  With  care  in  these 
respects,  the  condenser  will  be  satisfactory. 

The  Helix  for  this  set  of  instruments  should  be  made 
of  heavy  strip  copper  or  large  copper  tubing  and  should 
be  mounted  on  hard  rubber.  There  should  be  two 
stationary  and  two  or  three  variable  contacts. 

Oscillation  Transformer.  Better  than  a  helix,  how- 
ever, and  answering  the  same  purpose,  is  an  Oscillation 
Transformer,  which  gives  not  only  more  radiation, 
but  more  sharply  tuned  radiation.  This  instrument 
is  an  additional  transformer,  giving  greater  sharp- 


TRANSMITTING  APPARATUS 


27 


ness  jof  tuning  to  the  station  than  is  possible  with  a 
helix.  Instead  of  the  helix,  we  have  now  the  pri- 
mary of  the  oscillation  transformer,  which  inductively 
passes  on  the  oscillations  received  from  the  transmit- 
ting transformer  to  the  secondary  of  the.  oscillation 
transformer.  Through  this  process  of  induction,  if 
the  value  of  coupling,  i.e.,  the  distance  between  the 


HELIX 

two  coils,  of  the  oscillation  transformer  is  right, 
pure  trains  of  waves  are  given  off  the  aerial.  The 
advantage  of  giving  off  sharply  tuned  or  pure  trains 
of  waves  from  the  transmitting  station  is  that  they 
may  be  picked  up  with  less  interference  at  the  receiv- 
ing end.  These  pure  trains  of  waves  (see  Fig.  20) 
are  formed  by  attracting  to  the  same  apex  the 
apices  of  the  weaker  trains  of  waves,  which  would 


28   WIRELESS  OPERATORS'  POCKETBOOK 

otherwise  form  so-called  humps  in  the  wave  (see  Fig. 
21).  When  there  are  humps  there  may  be  several 
tuning  points,  at  the  crests  of  each  subordinate  wave. 
An  oscillation  transformer  may  be  built  to  advan- 
tage by  the  operator.  Both  primary  and  secondary 


FID  .  20 

should  be  of  soft  drawn  copper  ribbon  or  tubing  wound 
on  hard  rubber  or  some  other  material  of  as  high 
insulating  or  dielectric  strength.  There  should  be  one 
stationary  and  one  variable  contact  on  both  primary 
and  secondary. 

With  apparatus  like  that  here  described,  and  with 


F  i  &  .  ai 

suitable  aerial  and  ground  connections,  stations  may 
be  fitted  up  from  \  to  15  kw.  capacity.  We  shall 
add  detailed  lists  of  the  instruments  necessary  for  a 
few  sizes  of  transformers. 

Transmitting  Set  No.  j.     \  Kilowatt.    The  no- volt 
alternating  current  is  all  that  should  be  used,  although 


TRANSMITTING  APPARATUS 


29 


the  2  20- volt  current  may  be  used  with  specially  built 
apparatus.  If  direct  current  only  can  be  obtained,  an 
interrupter  must  be  added. 

The  Key  should  be  of  a  special  wireless  type  with 
heavy  contacts,  and  with  a  i-mf.  condenser  con- 
nected across  them. 

The  Transformer  may  be  of  either  the  open  or  closed 
core  type.  With  direct  current,  the  open-core  type 


COMPLETE  SET 

must  be  used  with  interrupter,  the  closed-core  type 
giving  little  or  no  efficiency  under  the  circumstances. 

The  Spark  Gap  should  have  contact  surfaces  of  silver, 
of  the  design  shown  in  Fig.  9. 

The  Condenser  should  have  twelve  or  eighteen  glass 
plates  8  x  10  inches. 

The  Helix  may  be  of  the  general  type  described  above, 
or,  if  desired,  an  Oscillation  Transformer  may  be  used. 

Transmitting  Set  No.  4.    |  Kilowatt.  The  same  power 


30        WIRELESS  OPERATORS'   POCKETBOOK 

requirements  as  in  Transmitting  Set  No.  3.  The  Key 
should  be  similar  to  that  in  Set  No.  3.  There  should 
be  a  transformer  of  J-kw.  capacity,  of  either  the  open 
or  closed  core  type.  The  Spark  Gap,  with  silver  con- 
tacts f  inch  in  diameter,  should  have  radiators  on 
both  arms.  The  Condenser  should  be  of  J-inch  glass 
and  should  consist  of  from  twelve  to  eighteen  sheets 
of  10  x  10  glass,  the  insulating  margins  around  the 
tinfoil  being  about  i|  inches.  The  Helix  should  have 
two  or  three  variable  contacts,  of  the  same  type  as 
in  Set  No.  3.  An  Oscillation  Transformer  would  be 
advisable. 

Transmitting  Set  No.  5.  i  Kilowatt.  The  same  power 
requirements  as  in  Set  No.  3.  The  Key  should  have 
very  heavy  silver  contacts,  of  special  i-kw.  design. 
The  Transformer  of  i-kw.  capacity,  of  either  open 
or  closed  core  type.  The  Spark-Gap  contacts  should 
be  one  inch  in  diameter,  and  with  radiating  surfaces. 
The  Gap  should  be  of  the  enclosed  type,  in  order  to 
muffle  the  noise  and  to  keep  the  injurious  ultra- 
violet rays  out  of  the  eyes.  The  Condenser  as  in  Set 
No.  4.  A  Helix  may  be  used,  but  a  i-kw.  Oscilla- 
tion Transformer  is  strongly  advised. 

Transmitting  Set  No.  6.  2  Kilowatt.  Power  re- 
quirements as  in  Set  No.  3.  A  Key  with  heavy 
J-inch  silver  contacts.  A  2-kw.  Transformer  of 
either  open  or  closed  core  type.  An  enclosed  Spark 
Gap  with  silver  sparking  surfaces  ij  or  if  inches  in 
diameter.  A  Condenser  constructed  in  units  so  that 


TRANSMITTING  APPARATUS  31 

it  may  be  connected  in  series  multiple  to  relieve  the 
dielectric  (or  insulating)  strain.  There  should  be 
thirty  to  forty  sheets  of  J-inch  glass,  10"  x  10"  in 
size,  and  immersed  in  castor  oil.  A  Helix  may  be 
used,  but  is  not  recommended.  The  2-kw.  Oscillation 
Transformer  is  necessary  to  stand  the  current. 

Transmitting  Set  No.  7.  5  Kilowatt.  Power  re- 
quirements as  in  Set  No.  3.  A  special  Key  with 
f-inch  silver  contacts  and  a  2-mf.  condenser.  A 
5~kw.  Transformer,  preferably  of  the  open-core  type. 
An  enclosed  multiple  Spark  Gap,  with  blow-pipe  or 
fan,  is  necessary.  Five  or  six  sparking  surfaces,  f 
inch  in  diameter  will  be  sufficient.  The  Condenser 
must  be  in  units,  with  twenty  to  forty  plates  of  J-inch 
glass,  14"  x  14",  and  with  2-inch  margins,  and  im- 
mersed in  castor  oil.  An  Oscillation  Transformer  of 
special  design  is  necessary. 


CHAPTER  IV 

THE    RECEIVING   CIRCUIT 

THE  transmitting  apparatus  is  always  engaged  in 
radiating  waves  from  its  aerial.  These  waves,  starting 
from  that  aerial  as  a  common  centre,  pass  on  in  ever- 
widening  circles,  as  do  the  ripples  in  water  when  a 
stone  is  dropped.  All  original  activity  is  confined  to 
this  process  of  sending  waves  from  the  transmitter, 
and  the  journey  of  the  waves  in  their  circles  is  as  far 
as  the  electrical  current  behind  the  transmitting  appa- 
ratus is  able  to  send  them.  But  another  process  is 
necessary  before  wireless  communication  is  established. 
Not  only  must  waves  be  sent  out,  but  there  must  be 
a  way  of  determining  what  signals  they  bear.  This 
is  done  by  stationing  another  set  of  instruments 
somewhere  in  the  circular  course  of  the  waves,  and 
this  second  set  of  instruments  must  be  able  to  reveal 
to  the  operator  the  meaning  of  the  signals.  This 
second  set  is  called  the  receiving  station.  It  must  be 
placed  within  the  radius  of  the  waves  sent  out  from 
the  transmitter,  but  the  nearer  it  is  to  the  sending 
instruments,  the  louder  and  clearer  will  the  signals 
be  received. 

32 


THE  RECEIVING  CIRCUIT  33 

Again  an  aerial  is  used,  but  instead  of  acting  as  an 
outlet  for  waves  generated  by  the  instruments  below, 
the  receiving  aerial  or  antenna  (just  as  the  antenna 
or  feeler  of  the  crab  informs  him  what  is  passing) 
conveys  to  the  operator  through  the  receiving  instru- 
ments news  of  what  is  passing.  Wireless  messages 
cannot  at  present  carry  any  secrets  of  importance,  for 
every  aerial  within  the  sending  range  of  the  transmitter 
will  carry  the  message  to  the  operator  below.  The 
electrical  current  necessary  to  radiate  wireless  mes- 
sages from  the  transmitting  aerial  is  very  great,  because 
the  waves  must  radiate  in  every  direction,  and  cannot 
be  confined  to  one  path  as  the  wire  of  a  wire  telegraph 
confines  its  current.  At  the  same  time,  the  power 
received  at  the  receiving  station  will  be  infinitesimal, 
for  the  very  same  reason  of  this  scattering  of  energy. 
Thus  it  is  necessary  to  have  the  most  sensitive  of 
receiving  instruments  in  order  to  detect  the  waves 
and  make  their  signals  known  to  us. 

The  two  absolutely  necessary  parts  of  the  receiving 
circuit  are  an  aerial  and  a  ground  connection.  The 
aerial  receives  or  picks  up  the  wave  signals  by  vibrating 
with  the  frequency  of  the  waves.  Thus  a  surging 
effect  is  set  up  in  the  aerial  between  air  and  ground. 
But  however  true  this  may  be,  we  must  add  other 
instruments  before  we  shall  be  able  to  discover  them. 
First  of  these  is  the  detector,  which,  as  its  name  implies, 
is  used  to  detect  the  presence  of  electric  vibrations 
in  the  aerial  circuit.  These  vibrations  or  oscillations 


34   WIRELESS  OPERATORS'  POCKET  BOOK 


may  be  detected  in  various  ways,  and  the  several 
different  detectors  work  on  quite  different  principles. 
As  the  mineral  forms  are  most  common,  and  are 
probably  the  most  efficient,  it  will  be  enough  in  this 


"RECEIVER 


FID. 


place  to  take  one  of  these,  the  silicon  detector.  When, 
in  a  detector  attached  to  an  aerial  circuit  through  which 
oscillations  are  surging,  a  point  of  brass  rests  against 
a  flat  surface  of  silicon,  it  will  allow  the  current  to 
pass  more  readily  in  one  direction  than  in  the  other. 


THE  RECEIVING  CIRCUIT 


35 


Thus  instead  of  the  alternating  current  set  up  by  the 
electric  waves,  we  have  a  rectified  direct  current 
passing  through  the  telephone  receivers  connected 


FID.  2.3 


across  the  detector.  By  this  means  we  hear  the  inter- 
mittent splashes  of  the  sending  key,  and  by  means  of  a 
recognized  code  we  are  able  to  form  words  from  them. 


36   WIRELESS  OPERATORS'  POCKETBOOK 


Thus  is  formed  the  simplest  receiving  circuit  (see 
Fig.  22)  which  will  be  capable  of  receiving  signals  of 
a  wave  length  comparable  with  our  aerial.  But  if 


Fl 


waves  of  greater  length  are  passing,  they  cannot  be 
picked  up  by  our  simple  aerial.  We  therefore  add  to 
its  (the  aerial's)  inductance  —  that  is,  to  its  time  of 


THE  RECEIVING  CIRCUIT 


37 


vibration  —  by  placing  a  coil  of  wire  in  the  aerial  cir- 
cuit.   A  variable  contact  on  this  " tuning"  coil  allows 


us  to  lengthen  our  oscillatory  circuit  in  accordance 
with  varying  wave  lengths. 

The  first  purpose  of  the  receiving  instruments  is  to 
make  it  possible  for  the  aerial  to  vibrate  in  harmony 
with  the  waves  it  picks  up.  The  tuning  coil  is  a  dis- 


38    WIRELESS  OPERATORS'  POCKET  BOOK 

tinct  addition  in  increasing  this  capability  of  tuning, 
but  another  instrument,  the  condenser,  adds  the 
second  improvement  in  this  respect.  The  effect  of 
the  condenser  is  similar  to  that  of  the  coil — it  adds 
capacity  to  the  circuit  and  makes  it  possible  to  balance 


the  circuit  with  the  frequency  of  an  incoming  wave. 
Fig.  24  shows  the  addition  of  a  condenser  of  fixed 
capacity  to  the  circuit,  and  Fig.  25  shows  the  further 
addition  of  a  variable  condenser.  This  latter  secures 
the  very  finest  adjustment  for  balancing  the  circuit. 

The  next  improvement  in  the  receiving  circuit  is 
to  remove  the  detector  circuit  entirely  from  the  aerial. 
This  is  done  by  using  an  oscillation  transformer  instead 


THE  RECEIVING  CIRCUIT  39 

of  a  tuning  coil.  We  have  now  two  entirely  separate 
circuits,  both  of  which  may  be  equally  balanced  to 
any  frequency,  and  which  are  connected  only  by 
induction  (inductively  coupled,  we  say).  The  primary 
of  the  oscillation  transformer  is  in  the  aerial  circuit, 
where  a  complete  oscillatory  circuit  is  made.  We  can, 
then,  vary  the  primary  in  the  aerial  circuit;  vary  the 
secondary  in  the  detector  circuit,  balancing  it  with 
the  primary;  and  we  can  vary  the  coupling  between 
the  two.  Then,  when  our  aerial  is  tuned  with  the 
incoming  wave,  and  the  secondary  circuit  is  balanced 
with  the  primary,  this  variation  of  coupling  enables 
us  to  cut  down  interference  from  stations  we  do  not 
want  to  receive,  and  at  the  same  time  to  bring  in 
more  clearly  those  stations  we  want. 

If  the  coil  in  any  of  these  circuits  is  inadequate  to 
receive  waves  from  any  desired  station,  another  coil 
may  be  placed  in  the  aerial  circuit  to  add  greater 
inductance.  Such  a  coil  is  called  a  loading  coil,  and 
may  be  used  as  well  with  an  oscillation  transformer  as 
with  an  ordinary  tuning  coil. 


CHAPTER  V 

RECEIVING  APPARATUS 

THE  receiving  station  is  usually  the  first  one  experi- 
mented upon,  and  might  more  properly  precede  the 
transmitting  station  in  our  description.  It  has, 
however,  been  thought  best  to  keep  to  the  logical 
order. 

The  instruments  necessary  for  a  receiving  set  are 
as  follows: 

Detector  Fixed  Condenser 

Telephone  Receivers         Variable  Condenser 
Tuning  Coil  Oscillation  Transformer 

The  Detector  is  the  most  essential  part  of  the  receiving 
apparatus,  and  its  purpose  is  most  vital  for  receiving 
wireless  signals.  The  waves  received  from  transmit- 
ting stations  are  picked  up  by  the  receiving  aerial.  As 
a  result,  an  alternating  current  of  very  high  frequency 
is  set  up  and  surges  in  the  aerial  and  the  receiving 
circuit.  The  detector  causes  this  exceedingly  feeble 
current  to  become  perceptible  to  our  ears,  by  means 
of  very  sensitive  telephone  receivers.  The  methods 
are  based  on  different  theories  according  to  the  type 

40 


RECEIVING  APPARATUS  41 

of  detector  used,  the  earliest  form,  the  coherer,  de- 
pending upon  a  quite  different  principle  from  that 
of  the  recent  mineral  detectors.  Some  forms  once 
used  have  been  discarded,  while  new  and  more  sen- 
sitive detectors  are  still  being  discovered.  We  shall 
mention  only  a  few  of  the  most  important  types, 
giving  them  in  their  historical  order,  which  has  proved 
to  be  the  order  of  their  respective  values. 

The  Coherer  is  mentioned  only  because  it  was  the 
earliest  form  used.  This  is  constructed  of  a  small 
glass  tube  with  two  highly  conducting  electrodes  of 


I \28L 


FID.2^  COHERE.* 

silver.  Between  these  the  space  is  partially  rilled  by 
a  mixture  of  nickel  and  silver  filings.  Large  filings, 
which  have  a  low  resistance,  are  used  with  relays  of 
low  resistance,  while  finer  filings,  lying  in  the  tube  with 
a  high  resistance,  are  used  with  relays  of  high  resist- 
ance. The  filings  have  normally  high  resistance.  When 
a  signal  is  received  from  a  transmitting  station  on  an 
aerial  or  oscillator,  an  electric  wave  conducted_to  these 
filings  breaks  down  the  resistance  caused  by  the  oxide 
existing  on  their  surface,  causes  them  to  cohere  and 
thus  lowers  the  resistance.  This  lowered  resistance 
and  the  consequent  more  perfect  path  for  the  current 
can  be  easily  detected  by  a  relay  which  is  in  the  circuit 


42        WIRELESS  OPERATORS'  POCKETBOOK 


with  a  battery.  This  relay  in  turn  may  be  coupled 
to  any  electrical  device,  for  instance  the  ringing  a  bell, 
lighting  a  lamp,  directing  a  torpedo  boat,  etc.  The 
coherer  of  this  principle  is  no  longer  'used,  other  and 
more  sensitive  detectors  having  taken  its  place. 

The  Carbon  Detector  was  a  transient  device,  used 
but  a  short  time  for  wireless  work.  It  would  be  hard 
to  find  one  to-day,  although  they  became  prominent 


CARBON       DLTECTOB 


only  a  few  years  ago.  It  was  an  improvement  over 
the  coherer,  being  somewhat  more  sensitive  and 
reliable.  It  is  often  called  a  microphone  detector. 
It  consists  merely  of  two  blocks  of  carbon,  upon  which 
rests  a  steel  needle.  The  pressure  of  the  needle  upon 
the  carbon  is  varied  by  the  pull  of  the  permanent 
magnet  underneath.  Adjustment  depends  upon  having 
an  imperfect  contact  between  the  needle  and  the 
carbon.  The  effect  of  electric  waves  upon  this  detec- 


RECEIVING  APPARATUS 


43 


tor  is  to  vary  the  resistance  between  carbon  and  needle 
and  to  indicate  this  in  a  telephone  receiver,  connected 
in  the  circuit  together  with  a  battery. 

The  Electrolytic  Detector  works  on  an  entirely  differ- 
ent principle,  and  was  a  great  improvement  over  the 
two  earlier  forms.  It  is  still  largely  used.  This 
detector  works  on  a  rectifying  principle.  It  may  be 


SEALED    POINT  BARE. 

FID.  29 


POINT 


constructed  in  two  ways,  the  sealed  point  and  the  bare 
point.  The  bare  point  has  a  fine  platinum  wire  for 
an  anode  which  rests  in  a  cup  of  dilute  nitric  acid. 
In  the  sealed  point  type  the  fine  platinum  wire  is 
sealed  in  a  glass  tube  with  its  lower  end  flush  with  the 
tube's  lower  or  sealed  end.  Both  forms  work  on  the 
same  theory,  which  is  shortly  this:  A  fine  platinum 
wire  just  touches  the  surface  of  the  liquid,  and  when 
a  slight  battery  current  passes  through  the  circuit, 


44         WIRELESS  OPERATORS'   POCKETBOOK 

bubbles  are  formed  at  the  wire.  If  the  adjustment  is 
just  right,  these  bubbles  will  continually  form,  thus 
making  a  gaseous  insulation  about  the  wire.  Now, 
if  there  is  an  aerial  and  ground  connection,  a  wave 
picked  up  by  the  former  becomes  a  feeble  alternating 
current  which  breaks  down  these  bubbles.  When  the 
circuit  between  acid  and  point  is  thus  made,  the  current 


SILICON  DETECTOR 

passes  through  and  may  be  detected  in  the  telephone 
receivers  connected  in  the  circuit.  At  the  same  time, 
the  acid  rushing  to  the  temporary  conducting  point 
starts  up  a  direct  current  which  is  perceptible  in  the 
receivers.  This  is  a  rectifying  effect. 

An  electrolytic  detector  is  more  easily  made  than 
purchased,  and  is  quite  as  likely  to  be  satisfactory. 
For  the  sealed  point  no  adjustments  are  necessary, 
but  the  bare-point  type  requires  very  fine  adjustments 


RECEIVING  APPARATUS  45 

indeed;  for  unless  the  wire  can  be  placed  exactly,  no 
effect  is  produced.  It  is  essential  that  a  battery  and 
potentiometer  be  used  in  circuit  with  either  form. 

The  Solid  Rectifiers,  sometimes  incorrectly  called 
Crystal  Detectors,  may  depend  upon  any  one  of  sev- 
eral different  minerals  which  have  been  proved  by  ex- 
periment to  have  rectifying  influence  upon  alternating 
currents  of  high  frequency.  It  is  thought  by  many 
that  this  is  aided  by  some  thermo-effect.  The  silicon 


r^>- 

/                         ^ 

FIG. 30 

detector  was  the  first  of  this  type  to  be  universally 
considered  successful.  It  is  still  one  of  the  most 
important  and  popular  ones.  Its  principle,  as  has 
already  been  stated,  is  that  of  a  rectifier.  No  battery 
is  necessary,  although  a  battery  and  potentiometer 
help  matters  along  to  some  extent.  The  silicon  detec- 
tor consists  of  a  flat  surface  of  highly  polished  silicon 
(the  flawless  kind  is  best),  upon  which  rests  a  brass 
point.  A  circular  or  spherical  piece  of  brass  resting 
on  the  flat  surface  of  silicon  makes  the  finest  contact 
of  all.  A  good  experimental  form  is  to  allow  a  sharp 


46   WIRELESS  OPERATORS'  POCKET  BOOK 

fragment  of  silicon  to  rest  upon  a  flat  surface  of  highly 
polished  brass.  The  detector  stand  should  be  so 
arranged  that  any  part  of  the  silicon  surface  may  be 


Sm                ^E~ 

\.    Ai-Tl               r 

V                                      \ 

FIB.    31 

used.  Its  simplicity  is  one  chief  advantage  in  favor 
of  the  silicon  detector.  No  special  care  is  necessary, 
and  its  adjustment  is  very  easily  made.  The  adjust- 
ment is,  however,  easily  broken  when  used  with  a 


FIG.   3£ 

transmitting  set.     Nevertheless  the  silicon  detector  is 
advised  for  all  general  purposes. 

A  very  good  solid  rectifier  or  mineral  detector   is 
the  Pyron  Detector,  which  also  works  on  a  rectifying 


RECEIVING  APPARATUS  47 

principle.  The  adjustment  is  harder  to  obtain  than 
with  silicon,  but  once  found  is  more  stable,  remaining 
for  months  at  a  time  in  a  very  sensitive  condition.  It 
works  with  a  brass  point  against  the  oval  fractures  of 
the  mineral  iron  pyrites,  sometimes  called  "fool's 
gold."  A  pyron  detector  stand  is  somewhat  different 


PERIKON  DETECTOR 

from  that  for  silicon,  the  cup  containing  the  mineral 
being  held  more  rigidly  by  a  pivot  and  screw,  so  that 
adjustment,  once  found,  may  be  retained. 

The  Perikon  Detector  is  now  generally  held  one  of 
the  best.  It  gives  far  more  sensitive  and  quick  ad- 
justment than  does  silicon,  and  retains  it  better.  It 
works  on  a  rectifying  principle.  The  perikon  detector 


48   WIRELESS  OPERATORS'  POCKET  BOOK 

consists  of  a  vertical  cup  into  which  are  fused  five  or 
more  fragments  of  zincite,  or  zinc  oxide.  Another  cup 
containing  a  fragment  of  chalcopyrite,  or  better  still 
of  bornite,  is  fused  into  a  cup  held  at  the  end  of  a 
rotating  rod  which  may  be  adjusted,  by  means  of  an 
inside  spring,  to  any  desired  pressure  against  the  zincite 
fragments.  The  zincite  best  for  this  work  occurs  in 


PERIKON-ELEKTRA  DETECTOR 

layers,  and  the  cross-section  of  these  layers  forms  the 
best  surface  for  adjustment.  A  pressure  of  from  \  to 
2  ounces  is  necessary  to  secure  the  best  results. 

A  very  recent  form  is  the  new  Perikon-Elektra 
Detector,  which  also  acts  on  the  rectifying  principle. 
This  detector  uses  a  micrometer  adjustment,  and  its 
stability  is  remarkable,  while  it  is  half  as  sensitive 
again  as  is  perikon.  This  is  Mr.  G.  W.  Pickard's 
latest  achievement  in  detectors. 


RECEIVING  APPARATUS 


49 


There  are  numerous  other  forms  of  detectors,  but 
those  already  described  are  the  best  and  most  sensitive. 
We  will,  however,  mention  two  or  three  others  in  pass- 


^ 


F  I  Q  .  3  3 

ing.  The  Tripod  Detector  (Fig.  33)  consists  of  three 
needles  resting  on  an  aluminum  plate,  and  works  on 
the  principle  of  partial  contact.  The  Carborundum 
Detector  is  a  crystal  form,  somewhat  less  sensitive 


=0 


FID.  3* 

than  silicon  (Fig.  34).    It  consists  of  a  piece  of  carbo- 
rundum resting  between  two  carbon  blocks. 

The   Magnetic   Detector  works   on   the  principle  of 


50   WIRELESS  OPERATORS'  POCKETBOOK 

diminution  of  hysteresis;  that  is,  on  the  principle  of 
the  sudden  drop  in  magnetism  caused  by  a  shock  to 
a  piece  of  shakily  magnetized  soft  iron,  and  its  con- 
sequent effect  in  producing  a  current  in  a  near-by  coil 
connected  to  a  telephone  receiver. 
A  battery  is  often  used  with  the  detector  and  is 


Fl  G.33- 


necessary  for  the  proper  results  with  a  coherer,  a  carbon, 
a  carborundum,  and  an  electrolytic  detector.  It  will 
also  increase  the  efficiency  and  aid  in  the  quick  adjust- 
ment of  the  silicon,  pyron,  and  perikon,  'but  should 
not  be  used  with  the  magnetic  or  perikon-elektra  forms. 
The  choice  of  a  detector  depends  largely  on  the  kind 
of  station  constructed.  For  general  experimental  pur- 
poses, silicon  is  most  adaptable.  The  electrolytic  is 


RECEIVING  APPARATUS 


51 


useful  and  very  reliable,  but  inconvenient  to  handle. 
The  patent  rights  on  pyron,  silicon,  and  perikon  detec- 
tors make  them  more  expensive,  however  much  they 
are  superior  to  other  forms. 
The  potentiometer  is   a   necessity  when   using   an 


FlCr. 


electrolytic,  carborundum,  carbon  detector,  or  coherer, 
and  an  advantage  even  with  a  mineral  detector.  Its 
purpose  is  to  vary  the  voltage,  and  thus  to  fix  a  definite 
amount  of  potential  necessary  for  the  best  advantage 


FIG. 


SLIDE 


of  the  detector  used.  The  potentiometer  may  consist 
either  of  German  silver  wire  or  a  stick  of  high-resist- 
ance graphite  connected  across  a  local  battery.  A 
slide  is  necessary,  and  if  desired,  the  potentiometer 
may  be  tapped  in  the  middle  and  a  lead  carried 


52 


WIRELESS  OPERATORS'  POCKETBOOK 


into  the  circuit.  The  advantage  of  this  last  is  that 
the  direction  of  the  battery  may  be  reversed  without  a 
pole-changing  switch. 

The  potentiometer  used  with  the  silicon  or  other 
rectifying  mineral  forms  may  be  of  less  resistance  than 
that  used,  for  instance,  with  the  electrolytic  detector. 
With  the  electrolytic,  about  300  ohms  resistance  and 
three  old  dry  cells  are  needed,  requiring  about  140 


BATTETW 


FI&.38 


feet  of  no.  32  German  silver  wire  or  90  feet  of  no. 
36.  With  the  silicon  and  other  detectors,  only  one 
cell  and  about  150  ohms  should  be  used. 

A  Testing  Buzzer  is  of  great  advantage  with  any 
detector;  it  generates  feeble  electro-magnetic  waves 
which  affect  the  detector  and  thus  enables  the  operator 
to  obtain  the  most  sensitive  adjustment.  A  small 
buzzer  is  best,  and  a  wooden  push  button  affords  the 
necessary  insulation.  Only  one  cell  and  a  small  con- 


RECEIVING  APPARATUS  53 

denser  are  needed.  The  diagram  (Fig.  38)  shows  the 
connection.  The  vibrator  point  (V)  or  better  the  point 
(A)  must  be  connected  through  the  condenser  (C)  to  the 
ground  (G).  The  condenser  should  be  about  six  square 
inches  of  tinfoil  on  each  side  of  a  sheet  of  waxed 
paper,  with  some  variation  of  size,  according  to  the 
strength  of  signals  desired.  It  will  be  observed,  how- 


HEAD  SET 

ever,  that  weak  signals  are  usually  best,  and  for  these 
a  small  condenser  is  needed. 

Telephone  Receivers  are  necessary  with  all  of  the  more 
recent  types  of  detectors,  in  order  to  make  perceptible 
minute  fluctuations  of  current.  For  wireless  work 
receivers  of  high  resistance  are  advisable,  and  up  to 
a  certain  point,  the  higher  this  resistance  the  more 
sensitive  the  receivers  are  to  feeble  currents.  Not 
that  a  great  resistance  makes  the  receivers  sensitive, 


54    WIRELESS  OPERATORS'  POCKET  BOOK 

but  that  a  very  large  number  of  turns  of  fine  wire 
around  the  magnet  influences  the  magnetism  of  the 
core  on  receiving  a  much  feebler  current  from  the 
detector.  Therefore  very  fine  copper  wire,  a  large 
number  of  turns,  and  their  nearness  to  the  core  are 
the  essential  qualities  of  a  wireless  receiver.  The 
classification  of  receivers  according  to  resistance  is 
merely  a  method  of  showing  the  number  of  turns  and 
the  fineness  of  the  wire  used;  i.e.,  the  sensitiveness. 
All  this  is  true  up  to  a  certain  point  only.  The  fineness 
of  wire  and  the  great  number  of  turns  used  to  wind 
receivers  of  over  3000  ohms  does  not  add  to  their 
sensitiveness,  the  current  dispersed  over  so  much  wire 
being  incapable  of  imparting  as  much  strength  of 
magnetism  to  the  core  as  in  the  case  of  receivers  of 
from  2000  to  3000  ohms  resistance. 

As  will  be  seen  from  what  has  gone  before,  receivers 
should  be  wound  with  single  covered  copper  wire. 
Enamelled  copper  wire  may  be  used  for  this  purpose. 
A  very  recent  receiver  wound  with  this  wire  held  inside 
a  tiny  spark  gap  in  order  to  prevent  burning  off  the 
insulation.  Some  unscrupulous  dealers  have  partly 
wound  the  magnets  with  German  silver  wire  in  order 
to  increase  the  resistance  of  the  receiver,  and  thus  to 
obtain  a  high  price  for  it.  It  will  be  understood,  how- 
ever, by  this  time,  that  such  a  receiver  is  no  better  if 
as  good  as  one  wound  with  the  same  number  of  feet 
of  copper  wire,  with  a  resistance  usually  one-thirteenth 
that  quoted  on  the  fraudulent  receiver  (the  resistance 


RECEIVING  APPARATUS  55 

of  German  silver  being  about  thirteen  times  as  great 
as  copper). 

The  receiver  cases  may  be  of  hard  rubber  or  alumi- 
num. A  composition  material  is  most  frequently 
used,  and  while  very  much  cheaper  is  more  brittle 
than  hard  rubber.  For  wireless  work,  a  receiver  must 
be  of  the  bi-polar  type,  the  single-pole  type  giving 
very  unsatisfactory  results.  The  diaphragm  may  be 
of  ordinary  thickness,  especially  in  a  receiver  of  a 
new  design  which  has  a  small  screw  to  adjust  the 
distance  between  diaphragm  and  magnets.  Thin 
gold-plated  diaphragms  are  sometimes  used  in  order 
to  secure  sharp  signals,  while  thicker  diaphragms  will 
give  signals  of  duller  tone.  Dull  signals  can  be  read 
in  spite  of  static  interference,  which  would  make 
sharper  signals  unreadable.  The  gold-plate  is  to  pre- 
vent rust,  but  lacquer  serves  the  same  purpose. 

The  head  band  for  the  receivers  may  be  of  nickelled 
brass  or  German  silver,  and  may  be  leather  covered 
for  insulation.  The  convenience  of  the  wearer  will 
determine  its  shape.  Sometimes  pure  gum  rubber 
tubing  is  put  over  the  head  band,  both  for  its  insula- 
tion, and  for  the  comfort  to  the  operator.  Rubber 
ear  cushions  over  the  receivers,  which  are  often  used, 
are  not  advisable.  They  increase  the  distance  of  the 
receiver  from  the  ear  and  may  weaken  all  very  faint 
signals. 

The  Tuning  Coil  is  a  device  by  means  of  which  the 
aerial  circuit  is  increased  (or  tuned)  so  as  to  receive 


56   WIRELESS  OPERATORS'  POCKET  BOOK 

incoming  waves,  whatever  their  wave  length  (train 
frequency).  The  tuning  coil  is  arranged  with  one  or 
more  variable  contacts  so  that  this  increase  in  the 
aerial  circuit  may  be  adapted  to  the  length  of  any 
waves  we  desire  to  receive.  The  tuning  coil  is  con- 
nected with  the  aerial  circuit  so  as  to  synchronize 
(or  time)  the  vibrations  of  the  aerial  with  the  wave 
length  or  train  frequency  of  the  transmitting  station. 
This  increase  to  the  aerial  circuit  does  not  depend 


TUNING  COIL 

entirely  upon  the  length  of  wire  contained  in  the  coil, 
but  upon  the  amount  of  coil  inductance  in  the  aerial 
circuit  or  inductively  coupled  to  it. 

A  tuning  coil  should  be  wound  of  soft  drawn  bare 
copper  wire,  approximately  no.  22,  on  a  core  of 
unshrinkable  highly  insulating  material,  such  as  hard 
rubber  or  cardboard  seasoned  or  soaked  in  shellac. 
Fibre  is  sometimes  used,  but  is  not  to  be  depended 
upon.  Bare  copper,  wire  is  best,  although  single 
covered  copper  wire  may  be  used  if  paths  are  cut 


RECEIVING  APPARATUS  57 

through  the  insulation  for  the  slides.  Enamelled  wire 
is  not  good  for  a  tuning  coil;  not  only  does  it  refuse 
to  maintain  its  close  tension  around  the  core  and 
become  loose,  but  the  enamel  acts  as  a  sort  of  condenser 
between  turns  because  of  its  extreme  thinness,  and 
makes  the  tuning  broader  or  less  definitely  sharp  than 
is  necessary.  The  wire  of  the  coil  must  be  well  insu- 
lated, by  winding  in  a  thread  cut  in  hard  rubber,  by 
spacing  it  on  a  screw-cutting  lathe  on  cardboard,  or 
by  winding  it  with  a  thread  between  each  turn.  Such 
a  coil  should  be  from  three  to  four  inches  in  diameter 
and  twelve  or  eight  inches  long.  There  is  no  advan- 
tage in  having  a  larger  coil,  as  the  wave  lengths  of 
practically  all  stations  come  within  this  range.  If  a 
greater  range  of  tuning  is  desired,  which  will  be  rare 
unless  for  the  extremely  long  waves  used  by  the  trans- 
atlantic stations,  it  is  better  to  have  a  loading  coil 
which  may  occasionally  be  switched  into  the  circuit, 
and  which  will  not  permanently  burden  it. 

One,  two,  or  three  variable  contacts  (slides,  sliders) 
are  used  on  tuning  coils.  Although  the  three-slide 
form  is  employed  for  its  greater  selectivity  and  to 
produce  a  loose-coupling  effect,  the  one  and  two  slide 
forms  are  most  popular  for  general  use.  The  slides 
should  have  a  phosphor  bronze  spring,  preferably  with 
a  rolling  contact,  and  a  well  insulated  handle. 

A  Loading  Coil  is  a  supplementary  coil  used  to  give 
a  greater  inductance  to  the  circuit,  and  thus  to  give 
it  a  greater  range  of  resonance,  and  to  enable  it  to 


58   WIRELESS  OPERATORS'  POCKET  BOOK 

receive  longer  waves  or  those  of  much  lower  frequency. 
In  form  it  is  merely  a  single-slide  tuning  coil. 

The  Condenser  collects  and  holds  electricity.  Its 
conductors  are  very  close  together,  and  adjacent  ones 
are  charged  with  opposite  kinds  of  electricity  —  one 
negatively  and  one  positively.  An  .alternating  current 
passes  readily  through  a  condenser,  because  the  charge 
keeps  changing  from  negative  to  positive  and  back 

ALTERNATING-         Dl"RECT 


again.  A  direct  current,  while  it  will  give  the  same 
initial  charge  to  the  first  plate,  cannot  pass  through 
the  condenser,  since  only  the  change  of  polarity  will 
maintain  the  charge  in  the  opposite  plate.  In  other 
words,  we  have  the  two  plates  of  a  condenser  (A  and 
B),  through  which  an  alternating  current  is  passing. 
When  A  receives  a  positive  charge,  it  repels  the  posi- 
tive charge  from  B  and  attracts  the  negative;  thus  B 
is  negative.  When  A  reverses  and  becomes  negative, 


RECEIVING  APPARATUS  59 

B  becomes  positive  for  the  same  reason.  The  same 
process  goes  on;  A,  constantly  changing,  forces  B  to 
change,  and  the  current  continues.  When  a  direct 
current  is  led  to  the  condenser  it  charges  A  positively. 
B  at  once  becomes  negative  and  remains  so.  There 
is  no  change  of  direction  in  the  current  after  the  first 
connection,  and  therefore  the  charge  remains  fixed 
and  no  current  can  pass. 

For  wireless  work,  there  are  two  kinds  of  condensers 


—  those  which  present  a  fixed  value  and  those  where 
the  condenser  value  may  be  varied  at  the  will  of  the 
operator.  The  former  is  called  a  Fixed  Condenser, 
the  latter  a  Variable  Condenser. 

A  Fixed  Condenser  is  used  in  order  to  balance  one 
part  of  the  circuit  with  the  other.  This  is  a  part  of 
the  process  of  tuning  or  bringing  the  circuit  into  resonance 
with  the  transmitting  station.  Practically  the  princi- 
pal use  of  a  fixed  condenser  for  receiving  is  to  short- 
circuit  (shunt)  the  telephone  receivers.  For  instance, 
in  the  circuit  shown  in  Fig.  40  the  high  frequency 


60   WIRELESS  OPERATORS'  POCKET  BOOK 

current  set  up  in  the  oscillatory  circuit  will  more 
.readily  pass  from  A  to  B  through  the  condenser  (C) 
than  through  the  receivers  (P),  since  the  latter  offer 
a  much  higher  resistance  to  it.  When  a  detector 
rectifies  the  high  frequency  alternating  current  to  a 
direct  current,  the  condenser  opposes  the  passage  of 
this  direct  current,  which  therefore  passes  through  the 
receivers  and  comes  to  our  ears.  A  fixed  condenser 
may  also  be  used  in  the  circuit  to  prevent  short- 


circuiting  the  detector,  when  the  latter  is  connected 
across  a  coil.  This  latter  connection  is,  however,  of 
less  advantage. 

The  capacity  of  a  fixed  condenser  ranges  between 
.002  and  .005  microfarads  (mf.).  Those  of  large 
capacity  should  be  used  with  telephone  receivers  of 
low  resistance,  of  smaller  capacity  with  receivers  of 
higher  resistance.  This  is  because  the  larger  wire  used 
in  the  low  resistance  phone  offers  an  easier  passage 
to  the  current  than  the  finer  wire  used  in  the  higher 
resistance  phone,  and  therefore  the  low  resistance 


RECEIVING  APPARATUS 


61 


phones  need  more  condenser  to  balance  the  circuit 
than  do  those  of  higher  resistance. 

Where  a  potentiometer  is  used,  it  should  be  short- 
circuited  by  a  fixed  condenser  and  be  placed  with  the 
phones  (see  Fig.  42). 

The  Variable  Condenser  is  used  to  enable  the  operator 
to  tune  or  bring  the  circuit  into  finer  resonance  than 
would  otherwise  be  possible.  If  the  point  of  sharp- 


F  I 


est  tuning  happens  to  come  between  the  turns  of  the 
coil,  and  where  it  cannot  be  reached  exactly  by  any  of 
the  slides,  the  variable  condenser  makes  it  possible 
for  the  operator  to  reach  the  exact  point  of  sharpest 
tuning,  and  thus  to  obtain  the  most  accurate  results. 

There  are  two  very  good  kinds  of  variable  condensers, 
the  Rotary  and  the  Slide  Plate  types.  The  Rotary 
type  is  the  easiest  one  to  manipulate  and  is  the  most 
convenient.  If  aluminum  plates  of  large  diameter, 
however,  are  used,  there  may  be  some  sagging  of  the 


62   WIRELESS  OPERATORS'  POCKET  BOOK 

metal,  which  will  cause  the  plates  to  short-circuit. 
The  Slide  Plate  type,  while  more  troublesome  to 
manipulate,  has  the  advantage  of  greater  stability, 
and  its  condenser  values  are  more  nearly  proportionate 
to  the  adjustment. 
The  plates  may  be  of  brass  or  aluminum,  and  of 


J 


ROTARY  CONDENSER 


stock  sufficiently  heavy  to  prevent  sagging.  For  this 
reason  brass  is  more  durable.  The  clearance  between 
the  plates  should  be  as  little  as  possible.  Many 
commercial  variable  condensers  have  a  clearance  of 
TjV  of  an  inch.  Those  with  ^  are  better,  but  are 
rare.  The  highest  capacity  of  a  variable  condenser 
should  not  be  over  .004  mf.,  .003  mf.  being  that  most 
often  necessary. 


RECEIVING  APPARATUS 


63 


An  Oscillation  Transformer  is  added  to  a  receiving 
set  in  order  to  obtain  more  selective  tuning  than  the 
ordinary  tuning  coil  will  give.  They  may  be  easily 


SLIDE  PLATE  CONDENSER 

made  and  at  small  comparative  expense.  They  are 
simple  to  operate,  and  generally  increase  the  receiving 
range  of  a  station. 

The   best   oscillation    transformers   are   wound   on 


OSCILLATION  TRANSFORMER 


64        WIRELESS  OPERATORS'   POCKET  BOOK 

threaded  hard  rubber,  both  primary  and  secondary. 
Next  to  hard  rubber  comes  shellacked  cardboard,  on 
which  the  wire  may  be  spaced  on  a  screw-cutting  lathe 
or  wound  with  thread  for  insulation.  In  size  the 
primary  should  be  about  four  inches  in  diameter  and 
four  inches  long.  No.  22  bare  copper  wire  should 
be  used,  twenty-four  turns  to  the  inch,  about  100 
turns  in  all.  One  slide  with  rolling  contact  on  the 
primary  is  necessary.  The  clearance  between  pri- 


mary  and  secondary  should  be  as  small  as  possible, 
not  more  than  I  inch.  The  secondary  should  be  about 
3!  inches  in  diameter,  and  the  winding  about  three 
inches  long.  Nos.  26  to  28  bare  or  single  silk  insu- 
lated wire  should  be  used,  about  200  turns  in  all. 
The  secondary  should  slide  in  and  out  of  the  primary, 
and  not  rotate  inside,  since  by  drawing  secondary 
away  from  primary  we  vary  not  only  the  magnetic  of 
the  two  coils,  but  also  the  mass  capacity  between  the 
two.  In  this  way  we  may  cut  out  static  effects  which 


RECEIVING  APPARATUS 


65 


interfere  with  our  receiving.  With  200  turns  on  the 
secondary,  taps  should  be  taken  out  every  twenty 
turns  and  brought  to  a  many-point  switch. 

By  the  addition  of  a  second  oscillation  transformer, 
using  a  circuit  like  that  shown  in  Fig.  44,  much  finer 
tuning  still  will  be  possible,  although  the  difficulty 
of  tuning  will  at  the  same  time  be  increased.  This  is 
called  a  Weeding-out  Circuit.  Indeed  it  is  possible 
to  add  another  oscillation  transformer,  to  gain  still 


finer  tuning,  and  at  the  same  time  make  tuning  more 
difficult.  Neither  of  these  circuits  will  be  used,  how- 
ever, except  where  the  interference  is  very  bad;  and 
then  only  seldom,  as  there  is  a  slight  loss  of  energy  as 
each  one  is  added. 

We  have  now  mentioned  all  the  usual  instruments 
for  receiving.  Only  a  few  out-of-the-way  or  merely 
experimental  forms  have  been  omitted,  and  those 
intentionally.  We  shall  now  give  a  selection  of  such 
sets  of  apparatus  as  are  well  fitted  for  use  together, 


66        WIRELESS  OPERATORS'   POCKET  BOOK 

and  which  will  be  adapted  to  certain  receiving  dis- 
tances, at  reasonable  prices. 

Receiving  Set  No.  i  with  Single  Slide  Tuning  Coil. 
Silicon  Detector;  one  8o-ohm  Receiver;  Fixed  Con- 
denser (.004  mf.);  Single  Slide  Tuning  Coil,  three 
inches  in  diameter  and  twelve  inches  long;  Two- wire 


COMPLETE  RECEIVING  SET 

Aerial  of  no.  12  or  14  copper  or  aluminum  wire,  50  feet 
long  and  50  high,  of  the  T  or  L  type.  For  receiving 
distance,  use  table  on  page  170. 

Receiving  Set  No.  2  with  Double  Slide  Tuning  Coil. 
Silicon  or  Electrolytic  Detector  and  Potentiometer; 
one  looo-ohm  Receiver  with  Single  Headband;  Fixed 
Condenser  (.003  mf.);  Double  Slide  Tuning  Coil,  same 


RECEIVING  APPARATUS  67 

dimensions  as  in  Set  No.  i;  Aerial  as  in  Set  No.  i. 
For  receiving  distance,  see  tables. 

Set  No.  3  with  Double  Slide  Tuning  Coil.  Silicon 
or  Electrolytic  Detector  and  Potentiometer;  two  1000- 
ohm  Receivers  and  Double  Headband;  Fixed  Con- 
denser; Double  Slide  Tuning  Coil;  Variable  Condenser, 
Slide  Plate  type;  Four- wire  Aerial,  50  to  75  feet 
long  and  60  feet  high,  of  no.  14  copper,  aluminum, 
or  phosphor  bronze  wire,  T,  L,  or  Fan  types.  For 
receiving  distance,  see  tables. 

Set  No.  4  with  Three  Slide  Tuning  Coil.  Silicon 
or  Perikon  Detector;  2ooo-ohm  Receivers,  as  in 
Set  No.  3;  Fixed  Condenser  as  in  Set  No.  2;  Three 
Slide  Tuning  Coil,  same  dimensions  as  in  Set  No.  i; 
Variable  Condenser,  either  Slide  Plate  or  Rotary 
type;  Aerial  as  in  Set  No.  3.  For  receiving  distance, 
see  tables. 

Set  No.  4  with  Oscillation  Transformer.  Perikon 
Detector;  Potentiometer;  two  i5oo-ohm  Receivers 
and  Headband;  Fixed  Condenser  (.0025  mf.);  Receiv- 
ing Oscillation  Transformer;  two  Variable  Condensers 
(.003  mf.  each).  The  receiving  range  of  this  set 
may  be  increased  practically  without  limit,  according 
to  the  type  of  aerial  used.  For  aerial,  see  Chapter 
VI  and  diagrams  on  page  71. 


CHAPTER  VI 

AERIALS    AND    GROUNDS!     TYPES    AND    CONSTRUCTION 

OF  first-rate  importance  in  constructing  a  wireless 
station  is  the  choice  of  a  type  of  aerial  and  a  good 
ground  connection  for  the  apparatus.  Ground  con- 
nections are  usually  easy  to  obtain  and  cause  little 
difficulty.  Not  so,  however,  with  the  aerial.  We  must 
select  a  type  of  aerial  suitable  for  our  surroundings, 
and  we  must  decide  upon  the  size  necessary  for  the 
transmitting  and  receiving  distances  we  wish  to  cover, 
and  we  must  consider  the  mechanical  difficulties  of 
construction,  the  cheapest  kind  of  wire  suitable  for  the 
necessary  spans,  and  the  proper  insulation  of  it. 

Any  aerial  which  can  be  used  for  transmitting  makes 
a  good  receiving  aerial.  The  converse  of  this  is  not 
always  true,  for  not  every  good  receiving  aerial  can 
also  be  used  for  transmitting.  Therefore  the  wireless 
operator  will  always  wish  to  construct  a  transmitting 
aerial,  and  those  described  in  this  chapter  are  of  this 
kind  and  may  be  used  indifferently  for  both  purposes. 
This  simply  means  that  there  must  be  a  number  of 
strands  and  that  the  extreme  height  of  the  aerial  is 
somewhat  less  than  its  length. 

68 


AERIALS  AND   GROUNDS 


69 


The  Straight-away  and  the  Loop  are  terms  used  to 
indicate  the  method  of  connecting  the  aerial.  In  the 
straight-away  form  all  the  upper  wires  end  dead  on 
an  insulator.  These  upper  wires  in  the  loop  form 
are  all  connected  together  and  divided  into  two  sec- 


STRAIGHT  AWAY 


LOOP 


PIG-.   *•  5" 

tions  at  the  bottom,  as  shown  in  Fig.  45.  Aerials  of 
almost  any  type  may  be  erected  in  either  form,  but 
while  the  loop  gives  slightly  better  results  on  a  short 
aerial,  the  straight-away  is  decidedly  the  more  efficient 
in  most  cases. 

There  are  about  six  types  of  good  aerials,  but  the 
combinations  of  these  are  almost  innumerable.     Each 


70        WIRELESS   OPERATORS'   POCKET  BOOK 


of  the  main  types,  however,  is  distinct;  and  it  seems 
best  to  confine  our  attention  to  their  principal  features. 
In  the  order  of  similarity  of  construction  these  are 


P  IT*  E  C  T  /  O 


O  F 


D-  T=\  El  R  T  El  S  T       EN/ER&Y 
PIG. 


the  r,  the   Vertical,  the  L,  the  F,  the  Faw,  and  the 
Umbrella  types. 

Of  all  these  the  T  is  most  nearly  perfect  and  gives 
the  best  results.  For  one  thing,  the  I  aerial  is  not 
directional  to  any  considerable  extent,  as  is  the  L  or 
the  V  type. 


AERIALS  AND  GROUNDS 


71 


T       RE.RIAL 


LOOP 


VERTICAL 


LOOP 


U  MBR  ELLA 
AERIAL 


V      A.E.RIAL 


FAN     AERIAL 


STRAIGHT 


1.0  OP 


DIAGRAM  OF  AERIALS 


72    WIRELESS  OPERATORS'  POCKET  BOOK 

After  the  J1,  the  Vertical  type  has  the  greatest 
advantage,  then  the  Umbrella,  the  Fan,  and  the  L 
or  F  types.  Questions  of  location  are,  however,  very 
important  in  making  this  decision  for  any  specified 
station,  and  may  almost  reverse  this  order. 

T  Type  Aerials.  For  all-around  work  both  in 
transmitting  and  receiving  the  T  type  is  generally 
considered  the  most  efficient.  For  the  very  best 
results  the  T  aerial  should  be  from  100  to  200  feet 
high  and  with  a  horizontal  stretch  of  from  90  to 
190  feet.  From  six  to  ten  strands  of  nos.  8  to  12 
wire  should  be  used  either  in  the  loop  or  straight- 
away forms.  These  dimensions  may  be  varied  if 
the  principal  of  a  horizontal  slightly  shorter  than  the 
vertical  is  adhered  to. 

Vertical  Type  Aerials  are  not  at  all  directional  and 
are  most  excellent  for  general  use.  They  may  be  in 
either  the  loop  or  straight-away  form.  This  aerial 
is  seldom  used  because  of  the  difficulty  of  erecting. 
One  very  long  pole  is  necessary.  It  should  be  from 
75  to  200  feet  high,  of  from  six  to  ten  strands  of  nos. 
8  to  12  wire.  . 

Umbrella  Type  Aerials.  These  are  always  good 
aerials  and  are  inexpensive.  They  must  be  in  the 
straight-away  form.  If  instead  of  a  pole,  water  con- 
ductor- pipes  are  used,  with  four  guy-wires  at  each 
joint,  and  both  pole  and  guy-wires  are  insulated,  the 
latter  with  strain  insulators,  the  whole  thing  may  be 
used  as  an  aerial,  and  is  very  efficient.  In  size  the 


AERIALS  AND  GROUNDS  73 

umbrella  aerial  may  be  from  50  to  150  feet.  The  guy- 
wires  will  have  to  be  proportional  to  the  height  of 
aerial  and  the  strain  upon  them.  Phosphor  bronze 
or  galvanized  iron  wire  should  be  used.  For  a  50- 
foot  pole  nos.  12  or  14  phosphor  bronze  would  be 
sufficient,  while  for  a  i5o-foot  pole  nos.  4  to  8 
stranded  steel  cable  is  necessary.  This  type  is  be- 
coming very  popular. 

The  L  or  Horizontal  Type  Aerial  may  be  either  in 
the  loop  or  straight-away  form.  It  has  the  disadvan- 
tage of  being  somewhat  directional.  It  should  be  about 
100  feet  long  and  100  feet  high,  with  eight  to  ten 
strands  of  8  to  12  wire.  This  type  is  very  common. 
It  has  often  a  length  of  200  feet  to  a  height  of  50  to 
75,  which  is  all  right  for  receiving,  but  is  objectionable 
for  sending. 

The  V  Type  of  Aerial  is  used  where  the  highest  point 
must  be  near  the  station,  with  a  lower  point  some 
distance  away.  This  type  is  especially  good  in  crowded 
quarters,  and  while  slightly  directional,  gives  excellent 
results.  It  should  consist  of  six  to  ten  strands  of 
nos.  8  to  12  wire,  about  100  feet  long  on  each  stretch. 
The  height  should  be  over  50  feet,  and  preferably  75 
feet. 

The  Fan  Type  is  especially  good  in  crowded  quarters 
also.  It  is  not  directional  and  must  be  of  the  straight- 
away form.  It  should  be  composed  of  from  fifteen  to 
twenty  strands  of  nos.  12  to  14  wire  and  should  be  from 
30  to  90  feet  high.  There  are  two  kinds  of  fan- type 


74    WIRELESS  OPERATORS'  POCKET  BOOK 

aerials  —  one  consisting  of  a  single  fan  suspended  be- 
tween two  poles,  the  other  formed  of  four  fans  sus- 
pended around  four  poles,  such  as  is  used  in  the 
Marconi  Station  in  Wellfleet. 

Almost  as  important  as  the  comparative  efficiency 
of  different  forms  of  aerials  is  the  fitting  of  those  types 
to  the  location  of  a  station.  All  the  surroundings 
must  be  considered  and  must  have  due  weight  in  the 
final  decision.  The  best  location  for  a  station  is  on 
a  hill  and  near  the  seacoast.  Directly  on  the  sea- 
coast  or  on  an  inland  hill  are  both  good  locations.  A 
wireless  station  in  a  forest  or  in  the  middle  of  a  large 
city  is  at  the  very  greatest  disadvantage,  since  the 
trees  and  the  trolley  lines  and  iron  frame  buildings  of 
the  city  absorb  waves  of  almost  any  wave  lengths  in 
use,  except  the  very  long  waves  of  a  few  such  stations 
as  Marconi  and  Fessenden. 

If  buildings  are  crowded  together  in  a  city  or  there 
are  near-by  trees,  the  umbrella  type  on  top  of  the 
building  will  probably  be  advisable.  Where  great 
height  cannot  be  obtained,  the  loop  form  should  be 
used.  The  fan  aerial  is  also  very  good  under  these  cir- 
cumstances. Long  wave  lengths  for  transmitting  are 
necessary  to  avoid  the  absorption  which  shorter  lengths 
would  undergo  amid  crowded  buildings. 

In  the  country  it  is  most  desirable  to  get  a  location 
on  a  hill-top;  and  if  possible,  one  free  from  trees.  If 
guy-wires  are  attached  to  trees,  a  series  of  strain 
insulators  should  be  placed  between  tree  and  aerial. 


AERIALS  AND  GROUNDS 


75 


MARCONI  STATION 


76        WIRELESS  OPERATORS'   POCKET  BOOK 

Copper  wire  is  the  very  best  for  an  aerial.  Next 
in  conductivity  comes  phosphor  bronze.  Phosphor 
bronze  wire  should  be  used  on  all  stretches  of  100  feet 
and  over.  Aluminum  wire  is  not  as  good  a  conductor 
as  copper,  although  some  of  the  larger  sizes  will  do 
just  as  well.  One  of  its  advantages  is  its  cheapness. 
It  is  very  light  also;  eight  or  ten  strands  of  aluminum 
wire  cause  very  little  strain  to  the  cross-arm.  Iron 
wire,  because  of  a  certain  reactance  effect,  is  a  poor 
conductor  and  should  not  be  used  in  the  regular 
aerial,  except  in  the  umbrella  type,  where  a  great 
number  are  used  in  multiple  as  guy-wires.  Only 
galvanized  wire  should  be  used. 

Following  is  a  list  of  the  best  sizes  and  materials  of 
wires  at  best  advantage  in  any  good  aerials. 

Size  (B  &  S) 

Copper  wire,  stranded,  solid,  or  tinned 8-14 

Phosphor  bronze,  stranded  or  solid   6-12 

Aluminum,  solid  6-12 

Galvanized  iron,  solid  (for  umbrella  type  only) 4-10 

Insulation  for  Transmitting  and  Receiving  Stations. 
The  proper  insulation  of  an  aerial  plays  a  very  im- 
portant part  in  the  transmitting  as  well  as  in  the 
receiving  distance.  One  of  the  greatest  faults  in  the 
experimenter's  transmitting  station  is  that  of  leakage 
from  improper  or  poor  insulation.  In  erecting  an 
aerial,  two  insulators  should  be  used  between  each 
wire  and  the  cross-arms.  Not  only  that,  but  the  ropes 
holding  the  cross-arms  and  all  guy-wires  should  be 


AERIALS  AND  GROUNDS  77 

protected  by  petticoat  strain  insulators.  The  follow- 
ing is  a  list  of  the  proper  insulators  for  transmit- 
ting powers: 

i  or  2  inch  spark  coil  ......  wire  cleats  or  spool  insulators. 

J  kw.  set  ...............  2  inch  strain  insulators. 

i    "       '    ...............  2    '      petticoat  strain  insulators. 

1  "      "    ...............  6    " 

2  "      "    ...............  6    " 

"      "    ..............  18    "  "  "  " 


To  ascertain  the  total  strain  (T)  upon  the  insulators, 
the  following  equation  may  be  used: 


T_ 

: 


ss 


where  L  is  the  length  of  wire  in  feet,  W  the  weight  per 
foot  in  pounds,  and  5  the  total  sag  of  the  wire  in  feet. 
For  example,  if  we  have  the  following:  Wire,  no.  6; 
weight  per  foot,  0.112  Ibs.  (with  insulators);  sag,  one 
foot;  span,  100  feet, 

(ioo)2  o.i  12       1120 

T  =  -  5—;  —    -  =  —5—  =  140  Ibs.,  total  strain  on 
o  X  I  o 

insulators. 

If  an  aerial  is  selected  and  erected  according  to  these 
principles,  the  operator  may  be  sure  that  he  is  getting 
approximately  all  the  efficiency  out  of  his  station. 
As  this  is  so  important,  he  should  take  great  pains  in 
each  part,  in  order  that  the  result  may  be  as  faultless 
as  possible. 


78        WIRELESS  OPERATORS'  POCKETBOOK 

Closely  associated  with  his  aerial  efficiency  is  the 
adequacy  of  his  ground  connections.  Although  a 
good  ground  is  nearly  always  easy  to  obtain,  care 
should  be  taken  in  assuring  oneself  that  it  is  a  good 
ground. 

The  ground  connections  for  sets  up  to  one  and  two 
kilowatt  should  be  made  to  water-pipes,  with  a 


WIRE 
TO     INSTRUMENTS 


V  X  t7^     jv;  s  \  \  \  \  XX N 


no.  6  to  8  insulated  wire.  In  all  cases  this  ground 
connection  should  be  made  at  or  near  the  street  side 
of  the  water-pipes,  or  where  it  enters  the  ground. 
Even  a  receiving  station  should  be  properly  grounded 
in  case  of  thunderstorms.  Gas-pipes  are  not  always 
an  efficient  ground,  because  they  do  not  always  form 
a  sure  connection;  a  certain  red  paint  used  in  the 
joints  sometimes  acts  as  insulator.  A  water-pipe,  on 
the  other  hand,  is  always  a  good  ground. 


AERIALS  AND  GROUNDS  79 

A  very  good  method  of  getting  a  ground  connection 
for  experimental  purposes  on  a  water-pipe  is  to  scrape 
the  pipe  well  and  bind  it  with  tin  or  lead  foil.  Upon 
this  is  wound  a  bright  piece  of  new  wire,  the  ground- 
wire.  Another  sheet  of  tinfoil  outside  is  then  covered 
with  tape,  if  it  is  to  be  used  permanently. 

Where  water-pipe  grounds  are  not  available,  several 
methods  may  be  resorted  to.  One  way  is  to  bury  a 
copper  ground  plate  in  charcoal  with  a  good-sized  lead 
(wire  6-8)  to  the  instruments.  Another  good  ground 
for  stations  near  the  water  is  to  throw  overboard  a 
large  metal  plate  securely  fastened  to  a  substantial 
lead  which  runs  to  the  instruments.  Still  another 
method,  and  the  best,  is  to  lay  several  hundred  square 
feet  of  wire  chicken  netting  over  charcoal  spread  on  the 
surface  of  the  ground.  This  can  be  used  even  on  sand, 
which  forms  the  poorest  connection  possible. 

When  an  efficient  aerial  and  a  good  ground  connec- 
tion are  secured,  the  operator  may  turn  his  attention 
to  the  installation  of  his  station,  which  we  shall  pro- 
ceed to  treat  in  the  following  chapter. 


CHAPTER  VII 

PROTECTION   AND  INSTALLATION   OF   A   STATION 

HAVING  assembled  all  the  separate  parts  of  the 
wireless  station,  when  the  aerial  has  been  erected  and 
a  good  ground  connection  made,  there  still  remains 
the  by  no  means  simple  task  of  assembling  them  and 
of  putting  the  completed  station  into  working  order. 
The  steps  in  this  process  are  first  the  protection  and 
then  the  installation  of  the  instruments  in  their  places. 
Protection  of  a  station  includes  both  its  preservation 
from  lightning  and  also  prevention  of  injurious  effects 
upon  the  lighting  system  or  the  metres  of  the  household. 
Installation  of  a  station  relates  to  the  wiring  of  the 
transmitting  apparatus  both  for  alternating  current 
and  for  direct  current  with  interrupters,  and  then  to 
the  placing  and  wiring  of  the  receiving  apparatus. 

Let  us  begin  with  the  aerial.  As  it  enters  the  station 
the  aerial  should  be  protected  by  a  one-piece  insulator. 
If,  for  instance,  the  wires  are  brought  through  the  outer 
wall  of  the  house,  one  continuous  containing  tube  of 
porcelain,  hard  rubber,  or  electrose  should  extend  four 
or  five  inches  beyond  either  surface  of  the  wall  to  stop 
any  leakages  of  current.  Small  porcelain  tubes  may 

80 


PROTECTION  AND  INSTALLATION  81 

be  used  on  spark  coils  operated  by  battery  current, 
but  an  electrose  or  hard  rubber  tube  one  inch  thick 
should  be  used  on  sets  of  from  J  to  i  kw.;  for 
stations  of  from  i  to  3  kw.  hard  rubber  or  electrose 
insulation  two  inches  thick  is  necessary;  while  for 
sets  up  to  5  kw.  electrose  insulators  at  least  three 
inches  thick  all  around  the  wire  will  be  needed. 
The  wires  for  all  leads  from  the  aerial  to  the  apparatus 


AERIAL. 


INSTRUMENTS 
\ 
i 


AERIAL     LEAT>  |OO   AMPERE. 

NO.  G»       V\/IT*E:  SW/ITCH 


X 


rNov«f  INSULATED 
FJG.^8  GROUND    WIRE 


should  be  of  no.  6  copper  wire,  rubber  insulated. 
Fire  Underwriters'  Rules  declare  that  all  aerial  wire 
going  into  a  station  should  be  connected  to  a  loo-am- 
pere  switch.  This  switch  should  be  of  the  single  pole 
double  throw  order,  with  the  aerial  connected  to  its 
centre  or  handle  pole.  It  is  advisable  to  use  a  double 
throw  switch,  since  the  instruments  are  entirely  cut 
out  when  the  aerial  is  grounded,  which  is  not  the  case 
if  a  single  throw  switch  is  used.  To  the  lower  pole 


82        WIRELESS  OPERATORS'   POCKET  BOOK 

should  be  connected  an  insulated,  no.  4,  ground  wire, 
joined  to  the  water-pipe  on  the  street  side  of  the 
water-metre,  or  to  one  of  the  ground  connections 
described  in  the  previous  chapter.  The  upper  pole  of 
the  loo-ampere  switch  is  connected  to  the  apparatus 
through  the  ordinary  switches.  In  cities,  Fire  Under- 
writers' Rules  order  that  this  switch  and  the  ground 


O 


<*  o 


SMALL  TO   110  VOLT 

SPARK    &AP  MAINS 


|H  5-   A/AP. 

y    FUSE 


FID.  *-<?  *  AVF-COND 


wire  be  placed  outside  the  station,  and  that  the  aerial 
be  grounded  when  not  in  use. 

The  protection  of  a  wireless  station  includes  the  safe- 
guarding of  the  line  and  metres,  of  the  key,  and  of  the 
step-up  or  transmitting  transformer.  For  direct  cur- 
rent, little  protection  is  necessary,  but  this  is  not  the 
case  where  alternating  current  is  used. 

Thorough  protection  of  the  line,  key,  and  transformer 
from  i  to  5  kw.  for  alternating  current  are  shown  in 
Figs.  49  and  50. 

The  sending  or  step-up  transformer  should  be 
shunted  with  two  5-ampere  fuses  and  one  2-mf.  con- 


PROTECTION  AND  INSTALLATION 


83 


denser  across  which  is  a  small  protective  spark  gap, 
the  whole  connected  in  series  across  the  primary  of 
the  transformer.  This  is  the  best  protective  device 
known,  and  will  prevent  all  kick-backs.  It  will  be 
found  advisable  to  use  a  i  or  2  mf.  condenser  across 
the  contacts  of  the  key,  where  these  are  not  large 
enough  to  prevent  its  sparking  or  sticking. 
The  proper  protection  for  the  line  is  shown  in  Fig. 


TO  TRANSFORME-R 

TO     TRAN5FOR/AE.R 

"*5T  tt/^NPl1!      TO    MAINS 
F  U  SC    U 

2M.F.IN         isi 

COND-  HJ  JSI 
fuSfTlj     T0    ^A»NS 

i 

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I     j 

S&     f*^ 
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2.  M»  F-  1 

i  ! 

5-  AMP.   FUSE  J 

TO    TRANS  FORttEB 

ro 

TRANSFOR/AER 

FHOTE.CTION    OF 

RWOTECTIOIM        OF 
*'C-      OC.MEBATOR 

F  I  G. 


50.  This  device  is  situated  near  the  metres  and  con- 
sists of  an  arrangement  similar  to  that  placed  across 
the  transformer;  two  5-ampere  fuses  are  connected 
in  series  across  the  main  line  with  a  2-mf.  condenser. 
Across  this  condenser  is  placed  another  protective 
spark  gap  with  a  distance  between  the  gaps  of  about 
^4  of  an  inch.  This  device  is  sufficient  to  protect 
the  line  transformer  and  metres  from  any  kick-backs 
in  the  circuit. 


84   WIRELESS  OPERATORS'  POCKETBOOK 

For  the  protection  of  an  alternating  current  generator 
it  is  necessary  to  use  a  more  complex  arrangement  of 
fuses,  condensers,  and  spark  gaps.  Across  the  gener- 
ator are  placed  two  5-ampere  fuses  and  two  2-mf. 
condensers  in  series.  Across  these  condensers  in  turn 
are  two  protective  spark  gaps.  A  connection  between 
the  two  condensers  is  grounded  through  a  third  2-mf. 


n — wwwv 


TRANSFORfNCR 


condenser.     This  device  is  especially  for  motor  gener- 
ator sets  and  affords  adequate  protection  there. 

With  direct  current  somewhat  simpler  safety  devices 
are  necessary.  Direct  current,  however,  is  not  nearly 
so  good  as  alternating  current,  for  some  kind  of  an 
interrupter  must  be  used  in  order  to  obtain  the  pul- 
sating current  described  in  Chapter  I.  Fig.  51  shows 
a  method  of  protection  for  direct  current.  The  key 
is  shunted  with  a  one  or  two  microfarad  condenser, 
while  the  main  line  has  two  5-ampere  fuses  in  series, 
with  a  condenser  and  protective  spark  gap.  This 
affords  sufficient  protection  for  ordinary  circuits. 


PROTECTION  AND  INSTALLATION 


85 


Installation.  A  broad  table  is  the  best  thing  for 
mounting  the  instruments  of  a  wireless  station.  If  this 
is  used  the  convenient  position  of  the  instruments  may 
be  easily  determined,  and  by  judicious  grouping  a 
slight  movement  of  the  hands  will  control  them  all. 
All  of  the  switches  used  in  changing  from  sending  to 
receiving  should  be  beside  the  key,  in  order  to  facili- 
tate the  operator's  movements.  The  most  convenient 

MAIN   CUT-OUT\ 


DE.TECTOB 


NSTALLATION 


OUTLINE.    OF 
F  I  C 


arrangement  places  the  transmitting  apparatus  at  the 
right  and  that  for  receiving  at  the  left. 

All  connecting  wires  for  the  transmitting  appara- 
tus should  be  rubber  insulated,  no.  14,  stranded, 
copper  wire.  Porcelain  or  hard  rubber  insulators  are 
necessary  where  the  wires  pass  through  the  table. 
Care  must  be  taken  in  wiring  underneath  the  table,  as 
well  as  on  top.  On  the  extreme  right  is  the  main 
cut-off  for  the  sending  instruments.  If  an  electrolytic 


86   WIRELESS  OPERATORS'  POCKET  BOOK 


interrupter  or  a  rotary  converter  is  used,  it  should  be 
encased  beneath  the  table,  where  it  will  be  out  of  the 
way.  Where  alternating  current  is  used  reactance 
regulators  will  cut  down  the  current.  With  sets  from 
2  to  5  kw.  these  are  of  the  best  advantage.  However, 
reactance  regulators  are  expensive  and  hard  to  build, 
so  a  bank  of  lamps  may  be  used  for  resistance  with 


6~ 
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TOTAL 

LAA\PS     USED 
FtCr. 


small  sets  using  either  alternating  or  direct  current. 
An  8-candle-power  lamp  allows  a  J-ampere  current 
to  pass;  one  of  16  c.p.  allows  J  ampere;  one  of  32  c.p. 
allows  a  full  ampere  to  pass.  If  we  want  a  current  of 
4!  amperes,  then,  we  place  in  the  circuit  one  64  c.p, 
two  32  c.p.,  and  one  16  c.p.  lamps,  thus  securing  the 
necessary  amperage. 

The  receiving  apparatus,  we  have  decided,  will  be 
on  the  left  of  the  table.     In  wiring  up,  rubber  covered, 


PROTECTION  AND  INSTALLATION 


87 


no.  1  6  or  18,  stranded,  copper  wire  will  be  necessary. 
The  leading  wires  of  the  receiving  instruments  should 
be  placed  on  top  of  the  table,  so  as  to  leave  the  under 
side  clear  for  the  transmitting  wiring. 


M  /=\T  1  M  Gr 


FI  &. 


All  leads  both  for  sending  and  receiving  apparatus 
should  be  as  short  as  possible.  For  these  and  the 
connections  the  operator  is  strongly  advised  against 
using  the  tinsel  telephone  cords,  their  resistance  being 
very  high. 

If  pains  are  taken  in  following  these  directions,  and 


88        WIRELESS  OPERATORS'   POCKET  BOOK 

a  careful  study  is  made  of  the  diagrams,  the  operator 
will  find  every  instrument  in  his  station  within  easy 
reach  of  his  hand.  Variations  may  sometimes  be 
advantageous  under  special  circumstances,  but  for 
ordinary  use  experience  has  shown  the  placing  of  every 
instrument  as  shown  in  the  diagrams. 

Fire  Underwriters'  Rules.  Following  are  the  regu- 
lations regarding  the  matter  issued  by  the  Fire  Under- 
writers: 

In  setting  up  wireless  telegraph  apparatus  (so  called), 
all  wiring  within  the  building  must  conform  to  the 
rules  and  requirements  of  the  National  Board  of  Fire 
Underwriters  governing  the  class  of  work  installed  and 
the  following  additional  specifications: 

I.  Aerial  conductors  to  be  permanently  and  effec- 
tively grounded  at  all  times,  when  station  is  not  in 
operation,  by  a  conductor  not  smaller  than  no.  4  B.  & 
S.  Gauge  copper  wire  run  in  a  direct  line  to  a  water- 
pipe,  at  a  point  on  the  street  side  of  all  connections  to 
said  water-pipe  within  the  premises;  or  to  some  other 
equally  satisfactory  earth  connection. 

II.  Aerial    conductors    when    grounded    as    above 
specified  must  be  effectually  cut  off  from  all  apparatus 
within  the  building. 

III.  Or  the  aerial  to  be  permanently  connected  at 
all  times  to  earth  in  the  manner  specified  above,  through 
a  short  gap  or  lightning  arrester;  said  arrester  to  have 
a  gap  of  not  over  .015  of  an  inch  between  brass  or 
copper  plates  not  less  than  i\  inches  the  other  way  with 


PROTECTION  AND  INSTALLATION  89 

a  thickness  of  not  less  than  f  of  an  inch  mounted  upon 
non-combustible  non-absorptive  insulating  material 
of  such  dimensions  as  to  give  ample  strength.  Other 
approved  arresters  of  equally  low  resistance  and  equally 
substantial  construction  may  be  used. 

IV.  In  cases  where  the  aerial  is  grounded  as  specified 
in  no.  I,  the  switch  employed  to  join  the  aerial  to  the 
ground  connection  shall  not  be  smaller  than  a  standard 
loo-ampere  jack-knife  switch. 

V.  Notice   of   wiring   done   for   these   installations 
should  be  sent  to  the  board,  the  same  as  for  all  other 
electrical  work. 


CHAPTER  VIII 

OPERATION   OF   A   STATION 

IF  good  care  is  taken  of  a  station,  it  will  generally 
work  to  its  highest  advantage.  The  operator  should 
see  that  his  apparatus  is  carefully  handled  at  all  times 
and  that  his  transmitting  apparatus  is  always  in 
proper  resonance.  This  chapter  will  take  up  not  only 
general  questions  of  care  of  instruments,  but  it  will 
deal  with  tuning  devices  suitable  both  for  fine  appa- 
ratus and  for  the  more  inexpensive  instruments.  Hints 
on  the  improvement  of  a  station's  working  will  be  no 
small  part  of  this  chapter's  interest,  and  in  this 
respect  we  are  now  coming  to  what  is  perhaps  the  most 
important  part  of  the  subject. 

No  general  suggestions  can  apply  both  to  transmit- 
ting and  receiving  apparatus,  since  the  range  of  distance 
covered  by  the  two  is  always  different:  Therefore 
we  shall  take  up  the  two  in  turn,  dealing  with  the 
separate  parts  of  our  subject-matter  first  as  applied 
to  sending  and  then  to  receiving. 

Transmitting  Apparatus.  The  working  of  the  station 
depends  largely  upon  the  care  that  is  taken  of  it,  and 
for  that  reason  apparatus  should  at  all  times  be  kept 

90 


OPERATION  OF  A  STATION  91 

free  from  dust.  This  is  especially  true  of  all  spark 
gaps,  the  large  one  used  for  transmitting,  and  all  small 
protective  gaps.  If  dust  collects  between  the  sparking 
surfaces,  it  acts  as  a  conductor,  the  gap  is  short- 
circuited,  and  then  the  fuses  blow  or  burn  out.  Once 
the  adjustments  of  the  spark  gaps  are  made,  these 
should  be  boxed  in  and  left  alone.  Wherever  also 
there  are  small  contact  points,  as  in  the  vibrator  or 
key,  a  particle  of  dust  may  cause  considerable  trouble. 

Operation  of  transmitting  apparatus  does  not  lie  in 
the  manipulation  of  the  key  so  much  as  in  tuning  up 
the  helix  or  condenser.  This  tuning  up  of  the  apparatus 
brings  the  helix  into  resonance  with  the  aerial  and  with 
the  condenser.  It  is  the  most  important  factor  in 
operation  and  is  one  requiring  skill  and  experience. 

The  theory  of  resonating  or  tuning  up  the  trans- 
mitting apparatus  is  as  follows:  The  helix  has  three 
contacts,  a  ground  connection,  which  should  be  sta- 
tionary, and  two  variable  connections,  one  in  series 
with  condenser  and  spark  gap,  another  leading  to  the 
aerial  (see  Fig.  55).  The  helix  is  thus  divided  into 
two  parts  or  inductive  fields,  one  included  between 
ground  and  condenser,  the  other  between  -ground  and 
aerial.  These  are  called  inductances  (L1  and  L2).  The 
aerial  ordinarily  acts  as  a  condenser  so  that  now  we 
have  two  groups  or  circuits,  consisting,  in  the  first 
place  of  the  aerial  condenser  (C2)  and  helix  inductance 
(L2),  which  act  as  a  secondary;  in  the  second  place  of 
the  condenser  (C1)  and  the  inductance  (L1),  which  act 


92    WIRELESS  OPERATORS'  POCKET  BOOK 

as  a  primary.     These  two  circuits  must  be  equalized 
to   secure   good   results,   i.e. 

C2xL2     =    ClxL\ 
secondary        primary 

Bringing   this   condition   about  by  manipulating   the 
helix  contacts  is  called  tuning. 

The  variation  in  the  condenser  (C1)  and  helix  (Ll) 
necessary  to  secure  the  same  value  as  the  aerial  (C2) 


n 


u 

FIG. 


and  inductance  (L2)  may  be  done  theoretically  either 
in  the  condenser  or  in  the  helix.  Practically,  however, 
it  is  so  much  easier  to  move  the  helix  contacts  than  to 
cut  tinfoil  off  the  condenser  plates  that  the  helix  is 
almost  always  made  variable,  the  condenser  stationary. 
Further,  it  is  necessary  to  notice  that  the  relative 
position  in  the  circuit  of  spark  gap  and  condenser  is 
unimportant  and  may  be  changed. 

There  are  several  methods  of  tuning  both  with  the 
helix  and  with  the  oscillation  transformer.     Two  spe- 


OPERATION  OF  A  STATION  93 

cial  instruments  are  used  in  tuning,  the  Geissler  tube 
and  the  hot-wire  ammeter,  the  latter  being  the  more 
efficient. 

The  Geissler  Tube  is  a  glass  tube,  in  both  ends  of 
which  are  sealed  electrodes,  generally  of  platinum. 
The  air  in  the  tube  being  exhausted  or  nearly  so,  a 
spark  will  readily  jump  between  the  metal  electrodes 
in  the  rarified  air.  If  a  slight  current  is  passed  through, 
a  faint  light  is  diffused  throughout  the  tube.  Increase 
in  its  light  marks  the  passage  of  a  stronger  current, 


F  I  D.  $-4 

and  the  maximum  brilliancy  marks  the  highest  point 
of  a  high  frequency  current.  A  Geissler  tube  of  plain 
design  is  shown  in  Fig.  56. 

The  Hot-wire  Ammeter  is  a  much  more  delicate 
instrument.  It  depends  upon  the  fact  that  a  German 
silver  wire  will  expand  when  heated  even  slightly. 
A  simple  form  is  shown  in  Fig.  57,  but  all  such  instru- 
ments work  on  variations  of  the  same  principle.  A 
German  silver  wire  is  stretched  between  two  points 
(A  and  B),  to  the  middle  of  which  is  attached  another 
wire  connected  to  the  end  of  a  fine  aluminum  needle 
(D).  This  needle  turns  on  a  pivot  or  fulcrum  (F)  and 


94        WIRELESS  OPERATORS'   POCKET  BOOK 

is  shown  on  the  dial  scale  (E).  Now  if  the  instru- 
ment is  connected  in  an  electrical  circuit,  a  slight 
current  passing  through  (A)  and  (B)  expands  the  g.s. 
wire,  which  lets  down  the  wire  (C)  and  causes  the 
aluminum  needle  (D)  to  deflect  from  the  point  of 


equilibrium  (o°).  Where  the  needle  shows  the  greatest 
deflection  will  be  the  point  of  greatest  current  strength. 
Since  the  ammeter  is  very  delicate,  a  variable  resist- 
ance should  be  shunted  across  it,  to  prevent  burning 
out  the  wire. 

The  first  step  in  tuning  is  to  move  the  condenser 
clip  (B)  on  the  helix  until  a  desired  wave  length 
is  obtained.  Thereafter  this  clip  will  remain  fixed. 


OPERATION  OF  A  STATION 


95 


Across  the  helix,  between  helix  and  aerial,  is  now  placed 
this  Geissler  tube,  which  shows  by  its  point  of  greatest 
brilliancy  the  exact  position  for  the  clip  (A)..  When 


AER  IAL 


n 


F  I  G  .,TS 


tuning-in  the  circuit,  the  light  in  the  tube  may  be 
lessened  in  intensity  by  decreasing  the  spark  gap. 
By  moving  the  aerial  clip  (A)  on  the  helix,  with  a  faint 
light  in  the  Geissler  tube,  it  will  be  easy  to  find  the 
point  where  a  perfect  balance  occurs,  by  the  maximum 


brilliancy  of  the  tube.     This  is  the  point  of  finest 
tuning  or  resonance. 

A  second  method  of  tuning  the  helix,  by  using  a 
hot-wire  ammeter,  is  better  and  more  exact  (Fig.  59). 


96   WIRELESS  OPERATORS'  POCKET  BOOK 

The  ammeter  should  be  placed  in  the  ground  circuit, 
or  between  ground  and  aerial,  the  former  method 
being  preferred  because  the  apparatus  can  then  be 
handled  if  necessary.  This  would  not  be  so  if  it  were 
in  the  aerial.  First  fix  the  wave  length  desired  by  the 
condenser  clip  (B).  Then  by  moving  the  aerial  clip 

(A)  up  and  down  the  helix,  we  find  different  degrees  of 
deflection  in  our  ammeter  needle.     Where  that  deflec- 
tion is  greatest,  the  current  is  strongest,  and  there  we 
will  place  clip  (A).     It  should  be  noted  in  both  cases 
where  tuning  up  with  a  helix  that  either  clip  (A)  or  (B) 
may  be  used  to  determine  the  wave  length,  the  varia- 
tion being  made  by  the  other  clip. 

With  the  oscillation  transformer  the  use  of  tuning 
instruments  is  much  the  same.  However,  it  is  possible 
to  secure  resonance  by  the  aid  of  a  small  auxiliary 
spark  gap,  and  without  special  instruments  when  a 
transformer  is  used  in  place  of  the  helix.  This  method 
is  shown  in  Fig.  60.  In  tuning  the  oscillation  trans- 
former, a  test  spark  gap  is  placed  across  the  secondary, 
i.e.  between  aerial  and  ground.  The  condenser  clip 

(B)  on  the  primary  of  the  transformer  sets  the  wave 
length.     The  secondary  is  tuned  with  the  aerial  clip 
(A).     By  operating  the  key,  and  at  the  same  time 
watching  the  discharges  at  the  auxiliary  spark  gap, 
we  will  find  where  they  are  most  rapid.     In  repeating 
the  process  the  point,  of  highest  resonance  may  be 
found.     This  method  of  tuning  is,   however,   by  no 
means  easy,  and  considerable  quickness  is  required  to 


OPERATION  OF  A   STATION 


97 


count  the  dots  of  the  key  and  at  the  same  time  note 
the  discharges  at  the  gap.  It  is  advisable  only  because 
of  the  simplicity  of  the  instruments. 

When  using  the  Geissler  tube  with  an  oscillation 
transformer,  it  should  be  placed  in  exactly  the  same 
position  as  the  auxiliary  spark  gap  shown  in  Fig.  60. 


The  maximum  brilliancy  will  show  the  point  of  highest 
resonance  for  the  secondary,  the  primary  determining 
the  wave  length  by  the  condenser  clip  (B). 

The  hot-wire  ammeter  is  placed  in  the  ground 
circuit  connected  with  the  primary  of  the  oscillation 
transformer  and  is  used  in  the  same  way  as  with  the 
helix,  the  condenser  clip  (B)  setting  the  wave  length 
as  in  previous  examples. 

Still  a  third  method  of  tuning  up  is  as  follows:  An 


98 


WIRELESS  OPERATORS1  POCKET  BOOK 


ordinary  ij-volt  Tungsten  lamp  placed  in  the  ground 
circuit  is  bridged  with  a  variable  resistance.  As  you 
press  the  key  and  at  the  same  time  vary  the  resistance, 
the  point  of  brightest  light  having  the  lowest  resistance 


FIG.  61 


will  show  best  value  of  balance  and  the  best  position 
for  clip  (A). 

The  coupling  between  primary  and  secondary  should 
be  carefully  regulated,  so  that  the  two  coils  be  far 
enough  apart  to  secure  sharp  tuning,  and  at  the  same 
time  be  near  enough  to  prevent  too  great  loss  of  energy. 
If  the  two  coils  are  too  far  apart,  they  will  lose  part 
of  the  inductive  effect  upon  each  other;  that  is,  they 
will  be  out  of  inductive  range.  If  they  are  too  near 


OPERATION  OF  A  STATION 


99 


together  the  secondary's  reactance  on  the  primary  will 
cause  a  hump  in  the  wave,  and  two  points  of  tuning 
will  be  the  result,  the  stronger  point  representing  the 
main  tuning  point,  and  the  weaker  one  showing  the 
split  or  division  of  energy. 

With  the  transmitting  instruments  perfectly  tuned, 


— L 


VERY    SMALL 
"RESISTANCE 


FID. 


\1    VOLT 
TUN  GSTE.N 


it  is  necessary  only  to  manipulate  the  key  quickly 
and  easily.  This  is,  of  course,  largely  a  matter  of 
quickness  of  movement  and  practice.  The  matter  of 
the  various  codes  now  in  use  will  be  further  discussed 
in  Chapter  X. 

Receiving   Apparatus.    The   operation   of   receiving 
apparatus  consists  principally  of  bringing  the  instru- 


100      WIRELESS  OPERATORS'  POCKET  BOOK 

ments  into  resonance  with  those  of  a  transmitting 
station  whose  messages  we  desire  to  receive.  In 
theory  the  tuning  of  receiving  apparatus  is  the  com- 
plement of  that  of  transmitting.  Waves  of  a  certain 
length  are  sent  out  from  the  transmitting  station,  and 
the  receiving  station  must  be  able  to  catch  them  on 
its  aerial  acting  again  as  a  condenser.  The  tuning 
coil,  acting  as  an  inductance,  is  joined  with  the  aerial 
and  enough  additional  condenser  value  to  balance  the 
incoming  waves.  This  condenser  value  may  be  sup- 
plied by  variable  or  fixed  condensers  added  to  the 
circuit. 

Operation  of  the  receiving  apparatus  includes  the 
manipulation  of  tuning  coils  and  oscillation  trans- 
former, of  the  variable  condenser,  and  of  the  detector 
in  order  to  secure  the  correct  amount  of  inductance 
and  capacity  (aerial  condenser  and  coil  inductance) 
to  receive  the  incoming  waves.  This  manipulation 
depends  upon  the  type  of  coil,  so  that  it  seems  best  to 
consider  the  tuning  of  each  one  independently.  In 
general,  it  may  be  said  that  the  slides  of  the  coil  or 
the  oscillation  transformer  should  first  be  brought 
roughly  into  tune  with  the  station  sending,  then  the 
variable  condenser  should  be  brought  to  the  point  of 
highest  resonance  before  adjusting  the  detector. 

The  Single  Slide  Tuning  Coil  is  most  frequently 
used  without  a  variable  condenser.  Under  such  cir- 
cumstances there  is  only  one  movement  to  be  made, 
one  slide  to  be  moved.  (Fig.  63.) 


OPERATION  OF  A 


101 


The  Double  Slide  Coil  should  be  used  with  a  variable 
condenser,  although  of  course  fair  results  may  be 
obtained  without.  The  clips  are  lettered  (A)  and  (B). 
A  rough  adjustment  is  found  with  (A),  and  this  is  made 
more  sharp  by  (B).  The  last  and  finest  adjustment  is 
made  with  the  variable  condenser  (VC).  (Fig.  64.) 


The  Three  Slide  Tuning  Coil  has  an  effect  similar 
to  the  Loose-coupled  coil,  but  it  is  not  so  selective;  i.e. 
it  will  not  bring  in  one  station  without  interference 
so  well  as  the  latter.  In  Fig.  65  are  shown  the  three 
slides;  the  ground  clip  (A),  between  which  and  the 
aerial  is  formed  a  primary  circuit;  the  distance  be- 
tween clips  (B)  and  (C)  forming  the  secondary  circuit, 
while  the  coupling  is  regulated  by  varying  the  distance 


102      WIRELESS  OPERATORS'   POCKETBOOK 

between  (A)  and  (BC).  The  first  adjustment,  which  is 
only  approximate,  is  obtained  with  (A).  Then  a  more 
careful  tuning  is  secured  by  moving  (B)  and  (C)  to- 
gether. The  finest  adjustment  is  then  made  with  the 
variable  condenser  (VC).  Finally  a  closer  adjustment 


of  (A)  may  be  made,  and  this  completes  the  tuning 
of  the  circuit. 

The  Loose-coupled  Tuning  Coil  or  Receiving  Oscillation 
Transformer  is  much  more  delicate  in  its  adjustment 
than  any  other  and  is  far  more  easily  manipulated. 
It  is  the  only  tuning  device  to  be  recommended  for 
good  work.  The  first  thing  is  to  obtain  the  desired 
station  roughly  with  the  slide  (A)  on  the  primary. 
Then  the  switch  (B)  on  the  secondary  should  be  varied, 


OPERATION   OF  A   STATION 


103 


followed  by  the  regulation  of  the  coupling  (K)  between 
the  two  coils.  After  this  the  variable  condenser  will 
be  adjusted.  And  finally  a  further  fine  variation  on 
the  primary  will  give  us  the  greatest  strength  of 
signals. 

The  Use  of  Two  Receiving  Oscillation  Transformers: 
The  Weeding-out  Circuit.     By  placing  a  second  oscilla- 


tion transformer  in  series  with  the  first  one  (see  Fig. 
67),  greater  selectivity  still  can  be  obtained,  although 
at  some  slight  loss  of  energy  in  the  strength  of  signals. 
The  first  adjustment  is  made  on  the  primary  (A). 
Then  either  (C)  or  (B)  should  be  moved  and  a  finer 
balance  found  with  the  variable  condenser  (D).  The 
slide  (E)  on  the  secondary  is  then  regulated  to  balance 
this  coil  with  the  previous  ones,  by  an  additional 


104      WIRELESS  OPERATORS'   POCKET-BOOK 

movement  of  the  second  variable  condenser  (F).  The 
tuning  is  so  sharp  in  this  circuit  that  it  is  necessary 
to  go  over  the  manipulation  of  these  variations  a  second 
and  even  a  third  time  to  secure  the  greatest  value. 

A  Tertiary  Weeding-out  Circuit  is  occasionally 
used  for  extreme  cases,  but  the  increased  loss  of  energy 
is  a  serious  drawback  to  its  usefulness,  except  where 


interference  is  unusually  bad.  Adjustment  is  made 
by  the  same  routine  as  in  the  first  weeding-out  circuit, 
with  the  addition  of  another  oscillation  transformer 
and  variable  condenser.  The  circuit  is  shown  in  the 
chapter  on  diagrams. 

The  Detector  will  be  used  in  every  case,  as  the  last 
and  final  adjustment.  If  the  surface  of  the  mineral 
in  a  silicon  or  perikon  detector  be  covered  with  a  thin 
film  of  Atlas  Oil  No.  2,  its  action  will  be  increased  and 
the  mineral's  rectifying  qualities  will  be  preserved. 


OPERATION  OF  A   STATION 


105 


Some  of  the  perikon  detectors  now  in  use  by  the 
government  show  the  mineral  entirely  immersed  in 
oil,  and  this  form  has  given  great  satisfaction  when 
used.  Molybdenite,  which  occurs  in  closely  packed 
layers,  should  have  a  sharp  knife-edge  resting  against 
the  cross-section  of  these  layers.  Good  silicon  should 


& 


be  free  from  flaws.  An  artificial  or  polished  surface 
is  the  best  for  contact  with  a  spear-point.  The  oval 
fractures  of  iron  pyrites  or  pyrop  should  come  in  con- 
tact with  a  spear-point  such  as  is  used  for  silicon. 
There  are  several  kinds  of  zincite,  only  one  of  which 
is  good  for  use  in  perikon  detectors.  This  occurs  in 
layers  of  some  thickness,  which  should  be  turned  edge- 
wise in  contact  with  a  sharply  pointed  piece  of  bornite, 
both  of  these  minerals  being  used  in  their  natural 


106   WIRELESS  OPERATORS'  POCKET  BOOK 

fractures.  By  adjusting  the  detector  carefully,  testing 
meanwhile  with  a  buzzer,  the  most  sensitive  point 
may  be  found;  and  this,  as  we  have  already  stated, 
should  be  retained  as  long  as  possible. 

Adjustment  and  operation  of  both  sending  and 
receiving  apparatus  is  of  the  highest  importance  for 
good  results  in  wireless.  The  importance  of  careful- 
ness and  fine  manipulation  cannot  be  over-emphasized. 
Recognition  of  this  and  the  skill,  which  are  learned  only 
after  considerable  experience,  show  the  division  be- 
tween the  real  operator  and  the  amateur,  in  the  worst 
sense  of  the  word. 


CHAPTER  IX 

BREAKING-IN     SYSTEMS!       METHODS     OF     SIMULTANEOUS 
RECEIVING  AND   TRANSMITTING 

IN  transmitting  wireless  signals  we  have  always 
the  sending  station,  from  whose  aerial  are  sent  out 
waves  of  a  definite  length  in  every  direction.  Now 
it  is  as  easy  to  receive  such  signals  to  the  north  as  to 
the  south  of  the  station,  the  only  limitations  being 
caused  by  the  limits  of  power  of  the  sending  station's 
electrical  apparatus  and  its  distance  from  the  receiving 
station.  Thus  all  wireless  messages  are  sent  out  in 
circles  around  the  transmitting  aerial.  If  there  are 
many  such  stations  close  together,  the  result  would  be 
pandemonium  but  for  the  fact  that  sending  stations 
may  regulate  their  wave  lengths  and  thus  avoid  inter- 
ference to  some  extent.  It  has  long  been  the  ideal  of 
wireless  experiment  to  find  some  method  by  which 
the  receiving  station  may  be  tuned  in  to  a  certain 
sending  station,  regardless  of  the  fact  that  other  sta- 
tions nearer  at  hand  and  perhaps  of  greater  power 
were  sending  at  the  same  time.  To  some  extent  this 
differential  tuning  is  now  possible,  but  only  in  cases 
where  waves  of  very  different  lengths  are  coming  in 
107 


108   WIRELESS  OPERATORS'  POCKET  BOOK 

at  the  same  time.  For  instance,  if  the  Marconi 
Station  (Cape  Cod,  Mass.,  with  a  wave  length  of  1800) 
is  sending  at  the  same  time  as  the  Charlestown,  Mass., 
Navy  Yard  (at  a  wave  length  of  from  320  to  560), 
a  receiving  station  in  Boston  will  be  able  to  cut  out 
one  or  the  other,  provided  he  has  a  Loose-coupled 
Tuning  Coil.  But  if  the  Navy  Yard  is  sending  at  the 
same  time  as  the  Board  of  Trade  Building,  Boston 


HAND  THROW  SWITCH 

(about  700  metres  wave  length),  it  will  be  almost 
impossible  to  tune  the  stronger  station  out  and  re- 
ceive only  the  weaker  one. 

If  tuning  devices  can  ever  be  brought  to  the  per- 
fection necessary  to  secure  such  fine  tuning  readily, 
every  wireless  man  will  be  glad.  But  meanwhile  we 
have  a  present  condition  of  affairs,  and  what  can  be 
done  to  obviate  interference  or  make  it  less  annoying 
is  every  man's  quest.  Breaking-in  Systems,  while  not 
yet  generally  popular,  seem  destined  to  supply  this 


BREAKING-IN  SYSTEMS 


109 


need,  and  are  increasingly  used  every  day.  If  they 
do  not  prevent  interference,  they  at  any  rate  make  it 
impossible  except  consciously. 

The  Breaking-in  System  is  a  method  of  simultaneous 
transmitting  and  receiving  wireless  signals;  that  is, 
a  device  is  placed  between  the  sending  and  receiving 
sets  so  that  the  operator  may  receive  incoming  signals 
even  while  he  is  sending  them  out.  This  device  con- 


SI/^XPLE    BRE.AK     KE.Y 
Fl  G.  6r 


sists  usually  of  some  attachment  to  the  key  which 
automatically  switches  in  the  transmitting  circuit 
every  time  the  key  is  pressed,  and  also  automatically 
switches  in  the  receiving  circuit  every  time  the  key  is 
released,  even  between  the  dots  and  dashes  of  the  code. 
Its  advantages  are  more  or  less  obvious  to  every 
operator.  To  the  government  or  any  commercial 
station,  the  breaking-in  system  has  the  advantage  that 
if  serious  interference  occurs  in  the  course  of  a  long 
message,  that  fact  may  be  signalled  to  the  sending 
operator.  Thus  the  latter  will  stop  until  elimination 


110   WIRELESS  OPERATORS'  POCKET  BOOK 

of  the  interference,  and  so  save  the  time  and  current 
which  would  otherwise  be  used  in  completing  a  message 
which  the  receiving  station  could  not  pick  up.  On 
the  other  hand,  a  breaking-in  system  will  notify  an 
experimenter  or  private  operator  when  more  important 


F  I  &.  69 


stations  are  sending.  He  will,  as  a  matter  of  course, 
stop  sending  with  wave  lengths  near  those  of  the 
professional  stations,  and  thus  will  cease  to  make  him- 
self a  nuisance  and  a  subject  for  hostile  legislation. 

Methods  of  breaking-in  are  determined  partly  of 
course  by  personal  choice,  but  much  more  by  the 
power  of  the  transmitting  apparatus.  Thus  we  will 
take  up  three  or  four  of  the  best  ways,  appropriate 
for  different  sizes  of  instruments. 


BREAKING-IN  SYSTEMS 


111 


112       WIRELESS  OPERATORS'   POCKET  BOOK 

For  a  One-inch  Spark  Coil  a  simple  mechanical 
device  is  all  that  is  necessary.  Such  an  arrangement 
is  shown  in  Fig.  68.  It  consists  of  a  short  strip  of  f 
inch  fibre,  half  an  inch  wide  and  four  inches  long,  and 
an  adjustable  contact  (A)  below  which  is  a  stationary 
contact  (B).  Fig.  69  shows  this  key  in  the  circuit. 
When  the  key  is  at  rest,  contact  (A)  will  be  on  contact 
(B),  thus  connecting  the.  aerial  with  the  receiving  set. 
On  pressing  the  key  (K),  the  contact  (A)  is  raised  away 
from  (B),  breaking  the  receiving  circuit.  Then  contact 
(C)  touches  (D)  and  completes  the  transmitting  circuit. 
The  device  must  be  adjusted  so  that  the  connection  of 
(A)  and  (B)  will  be  broken  before  (C)  touches  (D), 
otherwise  the  current  will  pass  into  the  receiving 
set,  breaking  down  the  detector  and  disturbing  the 
operator.  A  small  auxiliary  spark  gap  (E)  between 
helix  and  aerial  connects  the  latter  with  the  transmit- 
ting set  when  the  key  is  closed  and  insulates  it  from 
the  same  set  when  the  key  is  open. 

For  a  Two-inch  Coil  this  method  would  be  inade- 
quate. An  electrical  device  like  that  shown  in  Fig.  70 
is,  however,  suitable  for  such  a  coil  or  one  somewhat 
larger.  This  break  consists  of  an  insulating  rod  (B) 
supported  in  the  centre.  The  aerial  is  connected  to  con- 
tacts (C)  and  (D)  on  either  end  of  the  rod.  A  spring 
(E)  holds  the  rod  down  at  one  end,  the  receiving  end, 
where  the  circuit  is  made  through  contacts  (D)  and 
(F.)  The  opposite  end  of  the  rod  may  be  pulled  down 
by  an  electro-magnet  (H)  operating  on  an  armature  (J). 


BREAKING-IN  SYSTEMS 


113 


114      WIRELESS  OPERATORS'   POCKETBOOK 

When  this  end  of  the  rod  is  brought  down,  three  things 
occur:  the  contact  (D)  and  (F)  is  broken,  and  contact 
is  made  between  (C)  and  (L),  and  (M)  and  (N).  Fig. 
71  shows  this  device  in  the  circuit.  With  the  key  at 
rest,  the  spring  (E)  holds  the  contact  (D)  on  (F),  thus 
connecting  the  aerial  with  the  receiving  set;  the  con- 
tacts (MN)  and  (CL)  being  open  and  consequently  cut- 
ting out  the  transmitting  set.  If  the  key  (K)  is  pressed, 
it  operates  the  magnets  (H)  through  the  local  circuit. 
Then  this  magnet,  acting  on  the  armature  (J),  reverses 
the  pull  on  the  rod.  Now  contact  at  (D)  and  (F)  is 
broken,  and  the  receiving  side  is  cut  out.  Meanwhile 
connection  is  made  between  (M)  and  (N),  and  this 
turns  on  the  primary  current,  and  the  aerial  is  con- 
nected to  the  transmitting  side  through  the  contacts 
(C)  and  (L).  This  break  must  be  adjusted  so  that 
the  contacts  (D)  and  (F)  be  broken,  and  those  of  (C) 
and  (L)  made  before  that  made  at  (MN);  otherwise 
the  same  results  as  those  previously  mentioned  will 
follow,  and  the  operator  will  receive  a  shock. 

For  Transmitting  Stations  up  to  i  kw.  a  form  of 
break  permitting  greater  insulation  is  necessary,  and 
another  variation  of  electrical  device  has  been  arranged 
especially  for  small  transformers.  By  the  addition 
of  more  insulation  and  certain  protective  devices  this 
break  may  be  used  up  to  2  kw. 

In  the  break  (Fig.  72)  as  adapted  for  a  i-kw.  trans- 
former the  following  description  holds  good.  The 
key  (K)  has  two  sets  of  contacts  (AB  and  CD),  of 


BREAKING-IN  SYSTEMS 


115 


116      WIRELESS  OPERATORS'   POCKETBOOK 

which  the  latter  are  very  heavy.  When  the  key  is 
at  rest  neither  of  these  contacts  is  closed,  but  the  aerial 
is  connected  directly  with  the  receiving  side.  When 
the  key  (K)  is  pressed,  the  local  circuit  is  closed 
through  the  relay  (R),  thus  grounding  the  secondary 
of  the  oscillation  transformer  through  the  relay  con- 
tacts (E).  The  contact  (CD)  being  formed,  closes  the 
primary  circuit  and  operates  the  transformer.  It  is 
necessary,  as  in  previous  examples,  that  contact  (AB) 
be  made  before  (CD),  and  for  the  same  reason.  An 
adjustable  protective  spark  gap  (F),  consisting  of  two 
knife-edged  brass  plates  mounted  on  hard  rubber 
blocks,  is  placed  across  the  relay  contacts  (E)  for  pro- 
tection to  the  operator  in  case  the  contact  (CD)  should 
be  made  before  (AB). 

For  Stations  of  5  kw.  the  great  current  requires  very 
complete  protective  devices,  and  it  is  especially  neces- 
sary that  the  adjustment  of  the  detector  be  protected 
from  the  influence  of  the  powerful  transformer. 

This  form  of  break  is  shown  in  Fig.  73.  When  key 
(K)  is  at  rest,  the  contacts  (AB)  and  (CD)  leading  to  the 
transmitting  circuit  are  open,  and  the  aerial  is  connected 
to  the  receiving  set  through  the  contacts  (EF).  When 
the  key  is  pressed,  contacts  (AB)  close  the  local  relay 
circuit,  thus  grounding  the  aerial  by  contacts  (FH)  and 
protecting  the  detector  by  the  relays  (R^R2).  Just 
afterwards,  (CD)  being  closed,  completes  the  primary 
of  the  transmitting  circuit.  Contacts  (AB)  should  be 
made  before  those  of  (CD)  or  some  of  the  transmitting 


BREAKING-IN  SYSTEMS 


117 


118   WIRELESS  OPERATORS'  POCKETBOOK 

current  will  jump  the  contacts  (EF)  and  enter  the 
receiving  set.  However,  the  knife-edged  protective 
spark  gaps  (JJ),  previously  described,  are  used  to 
prevent  this  in  some  measure. 

Great  care  should  be  taken  to  protect  the  detector 
in  all  stations  of  over  i-kw.  capacity.  Even  the 
pyron  and  perikon-elektra  detectors  (whose  stability 
is  great)  will  not  retain  their  most  sensitive  points 
beside  transmitting  stations  of  this  size.  A  protective 
device  for  a  detector  is  shown  in  Fig.  74.  This  consists 
of  a  relay  operating  a  double  pole,  double  throw  switch 
to  cut  the  detector  out  of  the  circuit  entirely  when 
sending.  At  the  same  time  the  switch  closes  the 
receiving  circuit  so  that  no  influence  will  be  directed 
upon  the  detector,  which  is  screened  by  a  metallic  box 
(E)  having  two  leads  (AD)  insulated  by  hard  rubber 
bushings  (JJ).  The  connections  (AD)  project  beyond 
the  bushings  about  a  quarter  of  an  inch  to  serve  as 
contact  points  in  the  relay  device.  This  relay  device 
consists  of  a  magnet  (M)  which  acts  on  an  armature 
(H)  supporting  two  contacts  (BE)  which  are  insulated 
from  each  other  by  a  hard  rubber  standard  (K).  Two 
adjustable  contact  points  (C  and  F)  are  placed  to 
make  contact  with  (BE)  when  the  key  is  pressed.  Then 
these  points  are  strapped  together  or  short-circuited. 
The  operation  of  the  break  is  thus  simply  explained. 
If  the  key  is  at  rest,  the  magnet  (M)  is  dead,  so 
the  spring  will  hold  the  contacts  (DE)  and  (AB) 
closed,  connecting  the  detector  in  the  receiving  circuit. 


BREAKING-IN  SYSTEMS 


119 


120   WIRELESS  OPERATORS9  POCKETBOOK 

If,  on  the  other  hand,  the  key  is  pressed,  it  will  close 
the  local  circuit  and  excite  the  magnet  (M).  This 
pulls  the  armature  (H)  forward,  disconnecting  the 
detector  and  closing  the  receiving  circuit  by  contacts 
<B  and  C)  and  (E  and  F).  These  actions  break  the 
detector  from  the  circuit  and  leave  it  screened  or  pro- 
tected from  the  powerful  electrical  discharges  of  the 
transmitting  apparatus.  At  the  same  time  the  receiv- 
ing circuit  is  closed  and  this  prevents  any  influence 
upon  the  points  (AD)  which  might  occur  if  the  contacts 
(BE)  were  open  and  not  closed  by  CF. 

When  the  silicon  or  perikon  detectors  (zincite  and 
bornite  type)  are  used,  it  will  be  necessary  always  to 
use  this  protective  device  shown  in  Fig.  74,  the 
stability  of  these  detectors  being  poor  as  compared 
with  the  sealed  point  electrolytic,  pyron,  and  perikon- 
elektra  detectors.  Any  of  these  latter  forms  may  be 
used  on  stations  up  to  i  kw.  without  any  protection 
except  a  relay  to  short-circuit  them. 

Some  of  these  last  diagrams  may  seem  complicated. 
When  the  reader,  however,  stops  to  think  of  the  prob- 
lem of  switching  the  aerial  between  transmitting  and 
receiving,  while  at  the  same  time  protecting  himself 
and  the  instruments  with  a  single  movement  of  the 
key,  he  will  understand  why  such  care  is  taken.  It  is 
also  necessary  that  the  break  work  quickly  enough  to 
allow  incoming  signals  to  be  heard  even  between  the 
dots  and  dashes  of  an  outgoing  message. 


CHAPTER  X 

CODES 

CODES  are  merely  generally  recognized  systems  of 
short  and  long  signals,  "dots  and  dashes,"  arranged  to 
correspond  with  the  letters  of  the  alphabet,  numerals, 
and  punctuation  marks.  By  means  of  these  "dots 
and  dashes',"  a  sending  operator  is  enabled  to  spell  out 
messages  to  a  receiving  operator.  As  codes  are  only 
arbitrary  agreements,  it  might  be  possible  to  have 
as  many  as  there  are  operators  or  sets  of  operators, 
and  every  one  could  use  a  different  one.  In  practice, 
however,  it  has  been  found  convenient  to  use  certain 
generally  recognized  systems,  which  become  as  familiar 
as  a  language  to  every  telegraph  operator. 

There  are  three  of  these  systems  in  general  use  in 
America  —  the  American  Morse,  the  Continental,  and 
the  Naval  Codes.  The  most  popular  in  America  is 
the  Morse,  although  the  Continental  is  used  to  a  con- 
siderable extent,  especially  in  wireless  telegraphy.  The 
Continental  Code  is  generally  used  in  Europe,  and 
in  England  is  called  the  Morse,  while  that  code  called 
Morse  in  America  is  spoken  of  as  the  American  Morse. 
The  Naval  Code  is  used  officially  by  the  American 
Navy,  but  is  surpassed  in  popularity  by  both  the  other 

121 


122      WIRELESS  OPERATORS'   POCKETBOOK 


codes  even  in  the  Navy.     The  Continental  and  the 

Naval  Codes  have  one  point  of  similarity  in  that 

none 

of 

their  letters  are  spaced  (i.e.  include  spaces  as 

well 

as 

dots  and  dashes),  as  does  the  Morse.     The 

three 

are  shown  together  on  the  following  pages. 

THE  CODES 

MORSE                  CONTINENTAL              NAVY 

A 

.—                     A   ,_                        A    

B 

B    B    

C 

..     .                   C    C    ._. 

D 

D   D    

E 

E     .                              E     ._ 

F 

._.                     F     F    

G 

G    G    

H 

H    ....                        H    

I 

I     ..                            I     . 

J 

J     J     

K 

K   K    

L 

L     L    

M 

M  M    

N 

N    N    .. 

O 

.    .                       0    0    __. 

p 

P                                   P 

Q 

Q    Q    ._.. 

R 

.     ..                   R    ._.                        R    _.. 

S 

S     ...                         S    

T 

_                       T    _                           T    _ 

U 

.  U    ..__                        U    .  

V 

V     V     

W 

W  —                     W    

X 

X    X   

Y 

..  Y    __  Y    

Z 

..VT            z                         z 

CODES  123 


1  i i 

2  2 2 

3  3  3 

4  4  4 

5 5  5 

6  6  6 

7 .  7  7 

8  8 8 

9 9 9 

o o  o 


;==r.        H 

V?   ~"~ 

The  first  necessity  for  an  operator  is,  of  course,  to 
learn  thoroughly  some  one  of  these  codes.  As  the 
Morse  is  so  much  the  more  popular,  we  shall  take  that 
for  illustrative  material,  although  similar  groupings 
may  be  made  of  the  Continental.  Fig.  76  gives  a 
convenient  grouping  of  the  characters  which  adds  to 
quick  memorizing,  and  acts  as  an  aid  to  the  memory 
as  long  as  such  an  aid  is  of  use. 

A  CONVENIENT  GROUPING  OF  MORSE  CHARACTERS 
The  Dot      .      E  The  Dash     —     T 

ALL  DOTS 
CEHIOP          R          Y          Z  6 


124       WIRELESS  OPERATORS'   POCKET  BOOK 

ALL  DASHES 
L  M  T  5  o 


SPACED  LETTERS 
CORY 

FOR  MEMORIZING 
EISHP  6TL 


DASH  FOLLOWED  BY  DOTS 
N  D  B  8 

DOTS  FOLLOWED  BY  DASH 
A  U  V  4 

CONTRASTING  CHARACTERS 
AN          BV       CR      DU       FK      GW       J,       QX 

i !  •  !  I   : ;  .'  i  i .'  !  i  !  i  i  i 

:  i  i    !  i    i  i    !  : 

Since  every  word  in  telegraphy  must  be  spelled  out, 
certain  abbreviations  have  become  generally  recognized 
both  in  wire  and  wireless  telegraphy.  These  abbrevia- 
tions most  used  in  ordinary  telegraphy  have  usually 
been  adopted  in  wireless,  but  there  are  additions,  like 
the  famous  C.  Q.  D.  (S.  O.  S.),  for  special  wireless  needs. 
The  use  of  these  saves  considerable  time,  and  the  opera- 


CODES 


125 


tor  should  learn  to  use  them.     Every  line  of  business 

has  special  signs  used  frequently  in  its  own  business. 
We  include  here,  however,  only  the  general  abbre- 
viations, and  the  operator  will  make  his  own  special 
additions. 

ABBREVIATIONS 

3  or  30  Finish  signal 

73  Accept  my  compliments. 

ANS  Answer 

BK  Break 

CK  Check 

DH  Free 

FM  From 

GA  Go  ahead 

GE  Good  evening 

GM  Good  morning 

GN  Good  night 

HR  Another  message 

IMPT.  Important 

MIN.  Minute 

NM  No  more 

NO  Number 

OFM  Official  message  (used  only  by  the  navy). 

OK  or  II  All  right 

OFCorOFS  Office 

OPR  Operator 

PD  Paid  (generally  in  full). 

QN  and  .QJ  Beginning  and  ending  of  quotations. 

SIG  Signature 

SOS  International  distress  signal. 

SVC  Service 

V  Test  letter. 

X  or  99  Interference. 


126      WIRELESS  OPERATORS1   POCKETBOOK 

In  operating  a  wireless  station,  certain  forms  of 
messages  are  absolutely  necessary;  and  in  general 
practice  commercial  stations  have  adopted  those  forms 
used  by  the  ordinary  telegraph  companies.  Variations 
are,  of  course,  required,  and  the  following  message-form 
(Fig.  77)  will  answer  the  needs  of  any  commercial 
wireless  station. 

Such  a  form,  however,  is  rather  more  elaborate 
than  experimenters  will  ordinarily  require  for  private 
signalling.  For  such  operators,  nevertheless,  some 
formality  is  advantageous,  and  a  simple  question  and 
answer  form  like  the  following  may  be  adapted  to 
personal  needs. 

1.  Call  of  station  wanted  (three  times) CN,  CN.  CN. 

2.  Sign  call  of  sending  station  (once) VA 

3.  Finish  signal 3  or  30 

RECEIVING  OPERATOR 

a.  call  of  sending  station  (three  times) VA,  VA,  VA. 

b.  Sign  call  of  receiving  station  (once)  CN. 

c.  All  right OK.  OK. 

d.  Go  ahead GA .  GA . 

e.  Call  of  sending  station  (once) V  A 

f.  Sign  call  of  receiving  station C  N 

g.  Finish  signal   J  or  30 

SENDING  OPERATOR 

4.  Call  of  station  wanted  (three  times) CN.  CN.  CN. 

5.  Period  (repeated  two  or  three  times). . .  .Period.  Period. 

6.  Body  of  message    

7.  Period   Period.  Period. 


CODES 


127 


£ 
S 

X 

Vi 

'     d 

o 

g 

1 

M   9 

M 

tu 

N 

! 

C/5 

1 

S    H 

1 

S 

fc 

| 

W 

a 

E?l 

CO 

@ 

w 

M 

O 

H- 

J 

n 

o*        5 

n 

^   !?*                        en 
®x 

?l 

o 

p 

3  § 

O. 

£0    —  - 
C3  OQ 

I'§ 

r  H 

p  3 

*  S 

Q      O 

•       W 

C-(Ti 

K 

s"       >i 

w 

^    ^ 

?      ^ 

«> 

1  '*  - 

H 

ni      o^    ^ 

^^  ^ 

Co           "^ 

^    <j 

& 

^ 

HR  =  Message 

i  —  Number  of  Message 
SN  =  Sending  Station's  Call 

F  S  =  Sending  Operator's  Sign 


S  Y  =  Receiving  Operator's  Call. 
To  be  filled  after  the  message 
is  copied 


Ck  =  Check 

7  =  Number  of  words  in  body  of 
message 

Paid  =  The   message  may  be  either 
paid,  collect,  or  service. 


Time  =  To  be  filled  in  by  receiving 
operator,  after  the  message 
is  copied 


If  message  is  relayed 


FIG.  77 


128      WIRELESS  OPERATORS'   POCKET  BOOK 

8.  Sign  call  of  sending  station V  A. 

9.  Finish  signal 3  or  30 

RECEIVING  OPERATOR 

h.  All  right.  (If  message  is  received  and  understood} 

OK.  OK. 

i.  Call  of  sending  station V  A.  V  A- 

j.  Sign  call  of  receiving  station C  N.  C  N. 

k.  Finish  signal 3  or  30 

or, 

Question  (if  message  is  not  understood  and  must  be  repeated} 

DN.DN. 

i.  Call  of  sending  station V  A.  V  A. 

j.  Sign  call  of  receiving  station C.  N.  C  N. 

k.  Finish  signal 3  or  30 

SENDING  OPERATOR 

10.  All  right  (sending  operator  will  repeat) O  K.  O  K. 

11.  Call  of  receiving  station CN.  CN. 

12.  Sign  call  of  sending  station V  A. 

13.  Period    Period 

14.  Repeats  body  of  message,  and  ends  as  before  (8,  9) 


CHAPTER  XI 

THE  ETIQUETTE  OF  WIRELESS  AND  THE  SUBJECT 
OF  INTERFERENCE 

THE  air  is  free  to  all,  or  at  any  rate  it  has  been 
thought  so  until  discussion  upon  wireless  interference 
has  become  of  importance.  Now  we  have  the  knowl- 
edge that  in  England  a  license  fee  is  charged,  for  the 
use  of  the  air  presumably,  whenever  a  wireless  station 
for  transmitting  is  installed.  Many  bills  on  the  same 
subject  have  been  proposed  in  America,  but  up  to  the 
time  of  printing,  without  result. 

There  is,  moreover,  some  justice  on  the  part  of  those 
who  wish  to  limit  the  use  of  the  air  in  this  way.  Since 
the  loudness  of  signals  depends  upon  the  power  of 
the  transmitting  instruments  and  the  distance  to  be 
covered,  it  is  possible  for  private  persons  and  com- 
mercial companies  to  monopolize  the  space  in  certain 
vicinities,  so  that  a  most  important  government  mes- 
sage cannot  be  received.  It  is,  of  course,  to  be  under- 
stood that  the  government  should  have  right  of  way, 
not  only  in  the  roads,  but  in  the  air. 

Interference  may  be  of  two  kinds,  unintentional  or 
malicious.  In  their  effect  there  is  no  difference;  but 
129 


130  '  WIRELESS  OPERATORS'   POCKET  BOOK 

as  a  matter  of  fact,  it  is  the  unintentional  interfer- 
ence of  experimenters  unversed  in  the  code,  and  with- 
out adequate  breaking-in  systems,  that  has  given  rise 
to  most  of  the  legislation  hostile  to  them.  Malicious 
interference  either  on  the  part  of  an  experimenter  or, 
as  frequent  complaints  bear  witness,  on  that  of  com- 
mercial stations,  should  be  dealt  with  as  severely  as 
possible.  It  would  seem  that  license  restrictions  would 
be  too  mild  a  treatment  for  such  cases,  and  in  all 
probability  a  method  of  dealing  with  them  will  be 
evolved. 

In  cases  of  unintentional  interference,  there  is  usually 
no  remedy,  as  it  is  by  an  experimenter,  or  where  the 
'station  is  not  properly  equipped.  No  person  should 
operate  a  transmitting  set  until  he  has  a  proper  under- 
standing of  the  codes,  and,  if  he  has  no  breaking-in 
system,  without  listening-in  frequently  to  learn  whether 
other  stations  are  trying  to  make  themselves  heard. 
It  is  while  a  station  is  trying  to  receive  messages  from 
a  distant  source  that  interference  is  most  objectionable. 
While  a  powerful  station  near  you  is  sending,  a  sending 
station  of  less  power  or  different  wave  length  may 
send  without  troublesome  effect;  but  when  it  is  trying 
to  get  signals  from  a  weaker  station,  or  one  at  some 
distance,  your  interference  will  be  most  effective  and 
most  disastrous. 

There  are,  however,  some  methods  of  overcoming  in- 
terference. If  the  experimenter  will  use  an  oscillation 
transformer  for  sending,  he  will  be  able  to  tune  his 


THE  ETIQUETTE  OF   WIRELESS  131 

apparatus  much  more  sharply.  With  a  sharply  tuned 
wave  length,  he  will  be  received  only  by  apparatus 
tuned  in  with  his  instruments  most  exactly.  There- 
fore, if  he  is  from  fifty  to  one  hundred  metres  either 
above  or  below  the  commercial  station,  he  may  be 
tuned  out  without  trouble  at  the  receiving  instruments. 

Another  method  of  overcoming  interference  is  by 
the  new  duplex  system  of  wireless,  where  two  aerials 
are  used,  one  for  sending  and  the  other  for  receiving. 
The  shorter  aerial  is  for  sending,  thus  ensuring  a  short 
wave  length,  much  below  that  of  the  commercial 
stations.  The  longer  aerial,  for  receiving,  may  be  as 
large  as  is  desired  or  needed,  according  to  the  distance 
to  be  covered. 

Still  another  method  is  by  the  use  of  a  breaking-in 
system,  which  will  enable  the  experimenter  to  hear 
distant  sending  stations  when  they  call,  even  while  he 
is  sending. 

Where  interference  occurs  with  the  government  or 
commercial  stations,  a  weeding-out  or  third  (tertiary 
circuit)  should  be  used.  This  will  make  the  tuning  of 
the  receiving  instruments  twice  as  sharp  as  with  the 
ordinary  receiving  loose-coupled  transformer. 


wg 
c*  n 


Q  Q 
^  H 


132 


CHAPTER  XII 

WIRELESS   TELEPHONY 

THE  Wireless  Telephone  is  not  yet  a  success.  Vari- 
ous interesting  experiments  have  been  made  on  theo- 
retical principles,  and  for  short  distances  speech  has 
been  transmitted,  or  at  least  musical  tones  have  been 
identified.  Much  more  experiment,  however,  is  neces- 
sary before  it  will  be  possible  to  use  the  wireless  tele- 
phone even  to  the  extent  that  we  can  now  use  the 
wireless  telegraph. 

Distances  up  to  a  hundred  miles  have  been  claimed 
by  some  commercial  companies,  although  it  is  doubt- 
ful whether,  on  test,  telephone  transmission  has  been 
made  for  such  a  distance.  Moreover,  the  principle 
now  most  popular  with  experimenters  (the  so-called 
"arc  method")  does  not  promise  much  more  in  the 
matter  of  distance  even  under  the  best  of  conditions. 
For  short  distances,  however,  the  wireless  telephone 
has  been  used,  and  speech  has  been  distinctly  heard 
for  twenty  miles  certainly.  Any  greater  distance 
than  this  is  a  matter  for  proof  and  speculation.  This 
was  done  by  using  the  arc  method,  which  will  be 
later  described.  By  the  disruptive  discharge  method, 
133 


134   WIRELESS  OPERATORS'  POCKETBOOK 

greater  distances  can  easily  be  covered,  but  articula- 
tion is  poor.  Professor  Fessenden's  new  system  prom- 
ises improvement  in  both  respects. 

The  earliest  experiments  along  the  line  of  telephon- 
ing without  wires  were  devoted  to  what  we  now  call 


F  I  &.7S 

the  "conductive"  method  of  wireless  telephoning. 
The  connecting  medium,  in  this  case,  is  the  ground. 
The  diagram  (Fig.  78)  will  show  the  working  of  the 
system.  A  plate  (A)  buried  about  three  feet  below 
the  surface  of  the  earth  is  connected  through  a  set 
of  batteries  (B)  and  a  telephone  transmitter  (T)  by  a 
highly  insulated  lead-wire  to  another  plate  (J)  buried 


WIRELESS   TELEPHONY 


135 


in  the  ground  at  a  distance  of  some  fifteen  feet.  A 
duplicate  arrangement  on  the  receiving  side  leads  from 
a  plate  (A')  through  a  receiver  (R)  to  another  plate 
(JO-  When  a  current  is  set  up  in  the  transmitting 
side,  it  is  conducted  by  the  surface  of  the  earth  from 
A  to  A';  after  passing  through  the  metallic  connec- 
tions to  J'  it  will  find  its  way  back  again  to  J,  and  a 
circuit  will  be  established.  Now  if  we  speak  into  the 
transmitter  (T),  we  will  vary  the  current  over  this 


FIB. 


circuit,  and  our  speech  will  be  heard  in  the  receiver 
(R).  As  a  matter  of  fact,  the  conductive  method 
really  amounts  to  the  circuit  shown  in  Fig.  79,  the 
earth  forming  the  connecting  medium  between  both 
sets  of  plates.  This  method  will  work  up  to  about 
three  miles. 

Another  early  form  of  wireless  telephony  both  in 
point  of  original  experiment  and  of  electrical  impor- 
tance is  the  Static  Telephone.  This  form,  shown  in 
Fig.  80,  works  on  the  principle  of  the  condenser.  A 
wire  frame  or  grid,  consisting  of  lines  of  wire,  and 
having  the  effect  of  an  almost  solid  metallic  surface, 


136   WIRELESS  OPERATORS'  POCKETBOOK 


is  charged  through  an  induction  coil  by  the  human 
voice.  This  charge  on  the  grid  (A)  charges  a  second 
grid  (B),  which  is  connected  to  a  receiver,  and  the 
speech  is  distinctly  transmitted  by  electro-static  in- 
duction. The  effect  is  represented  in  our  second  dia- 


-T-  F  I  G.  8  O       -T- 

gram  (Fig.  81),  the  two  grids  acting  as  the  plates  of 
a  condenser.     This  will  work  up  to  a  half  mile. 

Still  another  form  of  wireless  telephone  works  on 
the  principle  of  the  induction  coil,  by  electro-magnetic 
induction.  (See  Fig.  82.)  A  loop  of  heavy  copper  wire 
about  five  feet  in  diameter,  connected  to  a  telephone 
transmitter  of  low  resistance  and  a  battery,  forms  the 


WIRELESS   TELEPHONY 


137 


transmitting  side.  The  receiving  end  consists  of  a  simi- 
lar loop  of  wire  attached  to  a  telephone  receiver,  which 
should  be  of  the  bi-polar  type,  and  must  be  wound 


with  about  no.  18  wire.  The  transmitting  side 
acts  as  the  primary,  the  distance  between  the  two 
loops  as  the  magnetic  field,  and  the  receiving  loop  as 
the  secondary  of  the  induction  coil.  It  is  to  be  noted 


that  in  both  instances  we  are  dealing  with  low  resist- 
ances. This  is  to  avoid  the  losses  of  energy  caused 
by  a  great  number  of  turns  of  wire  in  the  circuit.  For 


138   WIRELESS  OPERATORS'  POCKETBOOK 

the  same  reason  we  use  heavy  loops  of  wire,  a  low 
resistance  telephone  transmitter  and  receiver,  and 
batteries  in  series  multiple.  The  effect  of  this  form  of 
telephone  is  shown  in  Fig.  83.  This  will  work  up  to 
three  or  four  miles. 

The  smaller  illustrative  diagrams  (Figs.  79,  81,  and 
83)  show  in  graphic  manner  that  no  one  of  these 
methods  of  telephony  depends  upon  the  action  of  the 
high-frequency  waves  used  in  wireless  telegraphy.  In 
each  of  these  methods  the  plates  must  be  arranged  in 


F  t  & . 83 

a  certain  manner.  The  four  grounded  plates  used  in 
the  first,  conductive  method,  must  be  in  a  plane,  with  the 
upper  plates  at  a  similar  distance  underground,  and 
the  lower  plates  in  like  manner.  The  grids  of  the  static 
form  may  be  different  in  size  and  relative  position  above 
ground,  but  it  is  essential  that  the  transmitting  end 
be  higher  than  the  receiving.  The  loops  used  in  the 
last,  or  inductive  method,  must  be  either  in  the  same  or 
parallel  planes,  as  no  indications  will  be  received  if 
they  are  at  right  angles,  a  fact  true  of  the  induction- 
coil  principle. 
Although  none  of  these  use  detached  electro-mag- 


WIRELESS   TELEPHONY 


139 


netic  waves,  there  are  methods  of  wireless  telephony, 
or  rather  we  should  more  properly  say  Radio-tele- 
phony, which  do  make  use  of  those  waves.  Two  or 
three  of  these  wave  methods  are  of  importance,  and 
most  of  the  experiment  now  going  on  relates  to  them. 
First  of  these  is  the  Spark  Method.  In  passing 
from  our  description  of  the  wireless  telegraph,  this 


method  is  simplest.  It  may  be  used  with  an  ordinary 
transmitting  circuit  (Fig.  84)  by  the  addition  of  a 
telephone  transmitter  of  special  design  in  the  primary. 
The  vibrations  of  the  voice  speaking  into  this  transmit- 
ter are  stepped  up  to  a  higher  voltage  by  the  spark 
coil,  and  are  recorded  in  the  spark  gap.  This  gap, 
which  may  be  of  the  ordinary  form,  or  may  consist 
of  two  small  carbon  rods,  should  be  connected  in  an 
oscillatory  circuit  of  almost  any  design,  with  aerial  and 
ground  connections.  Fig.  85  shows  a  more  efficient 


140      WIRELESS  OPERATORS'   POCKET  BOOK 

form  of  telephone  working  on  the  same  principle. ,  This 
is  the  telephone  designed  by  the  author  and  consists  of 
a  special  telephone  transmitter  (A),  a  variable  impe- 
dence  (B),  connected  with  a  battery  (C)  in  the  primary 
circuit.  Any  vibrations  received  in  the  transmitter 
are  picked  up  by  the  secondary  and  are  discharged 
through  the  mercury- vapor  spark  gap  (D).  This 


LjJ 


discharge  in  the  mercury-vapor  tube  sets  up  oscilla- 
tions in  the  circuit,  which  in  turn  are  picked  up  by 
the  aerial ,  circuit  and  radiated  off  into  space.  Such 
a  telephone  will  transmit  messages  from  five  to 
fifteen  miles.  The  ordinary  tones  of  the  human 
voice  both  in  speech  and  in  singing,  and  the  notes 
of  musical  instruments,  especially  the  xylophone,  are 
revealed  very  clearly  through  this  mercury-vapor 
spark  gap,  but  articulation  is  sometimes  indistinct. 
The  Arc  Method  works  by  the  production  of  un- 


WIRELESS  TELEPHONY 


141 


damped  oscillations.  This  is  most  popular  at  present 
with  experimenters,  and  several  wireless  men  in 
America  are  working  with  it.  A  form  of  arc  generator 
shown  in  Fig.  86  consists  of  a  singing  or  musical  arc 
burning  in  hydrogen  gas.  This  arc  will  produce 
oscillations  when  connected  with  a  coil  and  condenser, 
thus  forming  an  oscillatory  circuit.  An  induction 


<±^/wwvwww — 

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FI&.  86 


coil  (A)  is  placed  in  the  power  circuit  between  the  arc 
and  the  power  supply.  In  the  primary  circuit  of  this 
is  placed  a  battery  and  a  telephone  transmitter.  The 
vibrations  of  the  voice  speaking  into  the  telephone 
transmitter  and  varying  the  current  about  the  arc 
cause  fluctuations  in  the  arc  corresponding  to  those 
in  the  transmitter.  These  variations,  communicated 
to  the  oscillatory  circuit,  are  picked  up  by  the  aerial 
circuit  and  radiated  from  the  aerial.  Speech  is  very 


142   WIRELESS  OPERATORS'  POCKETBOOK 

clear  when  using  this  method,  and  it  has  been  used 
up  to  fifteen  or  thirty  miles.  It  is  often  called  the 
speaking  arc. 

Another  arc  method  is  illustrated  by  Fig.  87,  con- 
sisting of  an  arc  generator  and  a  transmitter  in  the 


t 


FIO.  37 


aerial  circuit.  An  ordinary  direct  current  supply  is 
used  and  two  impedences  (JJ).  The  arc  (A)  is  water 
cooled,  in  order  to  keep  down  heat  disastrous  to  the 
production  of  oscillations.  This  arc  generates  best 
when  running  on  from  four  to  five  amperes  and  not 
over  220  volts;  anything  in.  excess  of  this  tending  to 
destroy  the  generating  properties  for  some  unknown 
reason.  The  arc  must  be  kept  at  its  greatest  length, 


WIRELESS   TELEPHONY 


143 


as  at  that  place  it  generates  best.  The  frequency  of 
the  arc  (A)  ranging  between  100,000  and  200,000  per 
second,  the  electro-magnetic  waves  follow  each  other 
so  closely  that  the  effect  upon  the  telephone  receiver 
is  continuous.  Now  if  we  speak  into  the  transmitter, 


placed  in  the  aerial  circuit,  the  vibrations  of  the  voice 
will  interrupt  these  waves,  and  the  interruptions  will 
be  audible  in  the  telephone  receivers  as  words.  This 
is  the  method  used  by  De  Forest.  Experiments  with 
this  system  have  covered  distances  of  perhaps  twenty 
or  thirty  miles,  due  to  the  limitations  of  the  current  in 
a  secondary  circuit. 


144      WIRELESS  OPERATORS'   POCKETBOOK 

Fig.  88  shows  Professor  Fessenden's  Wave-Gener- 
ator, one  of  the  latest  and  most  ingenious  methods 
yet  produced.  A  direct  current  dynamo  (A),  of  about 
5000  volts  potential,  is  connected  to  a  spark  gap  (S) 
through  a  variable  resistance  (R).  Across  this  gap  is 
placed  a  coil  (inductance)  (J)  and  a  condenser  (C). 
The  telephone  transmitter  is  placed  in  the  ground  cir- 
cuit. The  spark  frequency  of  this  device  is  governed 
by  the  resistance  (R),  so  that  we  can  jump  from  a 
frequency  of  one  spark  to  one  of  100,000  per  second. 
The  working  theory  of  this  plan  is  that  the  current 
from  the  dynamo  flowing  through  the  circuit  slowly 
charges  the  condenser  through  the  resistance  (R). 
When  a  charge  in  the  condenser  becomes  great  enough 
to  overcome  a  set  distance  between  the  gaps,  a  spark 
will  jump  across  and  will  excite  a  current  in  the 
oscillatory  circuit.  The  greater  the  resistance  in  the 
circuit,  the  longer  it  will  take  to  charge  the  condenser, 
and  the  fewer  the  sparks  per  second  across  the  arc. 
If  the  resistance  is  low,  on  the  other  hand,  the  con- 
denser will  charge  and  discharge  itself  very  rapidly 
across  the  gap.  When  a  frequency  of  from  80,000  to 
160,000  is  obtained,  the  waves,  following  so  rapidly, 
are  inaudible  at  the  receiving  end,  and  an  almost 
continuous  current  is  made.  The  vibrations  of  the 
voice  speaking  into  the  transmitter  interrupt  or  vary 
the  intensity  of  the  continuous  waves,  and  speech  is 
thus  transmitted. 

In  all  forms  of  wireless  telephony  a  special  kind  of 


WIRELESS   TELEPHONY 


145 


transmitter  is  not  only  advisable,  it  is  actually  almost 
necessary.  There  has  been  considerable  experiment 
as  to  the  kind  of  transmitter  best  adapted  to  the 
purpose,  and  numerous  modifications  of  the  ordinary 
transmitter  are  the  result.  A  type  which  can  be  used 


FID.8S 


with  all  the  methods  of  telephony  described  is  shown 
in  Fig.  89. 

This  transmitter,  which  is  of  the  inertia  type,  works 
very  well  for  all  experimental  purposes,  although  for 
permanent  use  the  solid  back  type  might  perhaps  be 
advisable.  This  inertia  transmitter  should  have  a 
very  massive  frame  of  the  ordinary  type  for  long 
distance  use.  The  diaphragm  (B),  about  .006  inch 
in  thickness,  of  French  steel,  should  be  held  firmly  in 


146      WIRELESS  OPERATORS'   POCKET  BOOK 

place  by  a  metallic  ring  (C).  The  mouthpiece  (D), 
of  ordinary  type,  must  be  so  arranged  that  the  distance 
between  it  and  the  diaphragm  may  be  varied.  The 
transmitter  button  (E),  attached  to  the  centre  of  the 
diaphragm,  is  shown  separately  in  Fig.  90.  This 
button  consists  of  a  cup  or  carbon  chamber  (A), 
an  insulated  face-plate  (B),  and  a  cap  (C).  The 
carbon  chamber  (D)  and  the  face  plate  (E)  should  be 
made  of  platinum,  although  silver-plated  brass  is 


F)  G  .  90 

very  good.  The  inside  diameter  of  the  carbon  chamber 
(D)  should  be  about  f  inch,  while  the  distance  between 
the  back  of  this  chamber  and  the  face  plate  should  be 
|  inch  when  the  cup  is  closed.  The  face-plate,  backed 
with  a  thin  mica  washer  (F),  which  supports  and 
insulates  it,  is  held  in  place  by  the  cap  (C).  The 
carbon  granules  will  be  large  and  globular  when  used 
in  the  primary  circuit,  and  the  chamber  should  be  well 
filled  with  them.  When  used  in  the  aerial  circuit 
they  should  be  much  smaller  and  should  only  partially 
fill  the  chamber.  The  thinness  of  the  mica  washer  is 


WIRELESS   TELEPHONY  147 

of  importance,  in  order  to  ensure  the  greatest  amount 
of  vibration  reaching  the  granules. 

For  receiving  wireless  telephone  messages,  any  of 
the  detectors  and  any  of  the  receiving  circuits  shown 
in  the  back  of  the  book  may  be  used  successfully. 


APPENDIX 


AERIALS 

The  T,  the  Vertical,  the  Umbrella  are  the  best  types  of  aerials. 

The  L,  the  V,  the  Fan  are  all  good  types. 

Combinations  of  types  are  often  best  fitted  for  a  specific  location. 

TRANSMITTING  CIRCUITS.    I 

1.  Spark  Coil,  Spark  Gap.     The  simplest  circuit. 

2.  Spark  Coil,  Spark  Gap,  Condenser.     The  addition  of  a 
condenser  to  give  a  longer  wave. 

3.  Spark  Coil,  Spark  Gap,  Helix.     Addition  of  a  helix  to  give 
longer  wave. 

4.  Spark  Coil,  Spark  Gap,  Condenser,  and  Helix.     The  com- 
bination of  instruments  for  the  best  results. 

Any  of  these  circuits  may  be  used  on  a  one-inch  spark  coil 
for  distances  of  from  one  to  two  miles;  but  they  are  not  practical 
for  greater  distances,  and  do  not  give  the  full  value  of  the  instru- 
ments. 

TRANSMITTING  CIRCUITS.     II 

5.  Spark  Coil,  Spark  Gap,  Helix,  and  Condenser.     A  practical 
circuit  for  a  3-contact  helix. 

6.  Spark   Coil,   Spark   Gap,   Helix,    Condenser,  and   Anchor 
Gap.     For  use  with  loop  aerials  and    breaking-in  systems.     A 
practical  circuit. 

149 


150  APPENDIX 

7.  Spark  Coil,  Spark  Gap,  Condenser,  3-Contact  Helix.     A 
popular  and  practical  circuit. 

8.  Spark  Coil,  Spark  Gap,  Condenser,  4-Contact  Helix.    Circuit 
especially  adapted  for  the  variety  of  its  effects. 

All  practical  circuits. 

TRANSMITTING   CIRCUITS.     Ill 

g.  Transformer  or  Spark  Coil,  Spark  Gap,  Condenser,  4- 
Contact  Helix,  and  3-Point  Anchor  Gap.  For  use  with  loop 
aerials.  As  practical  as  any  circuit  using  a  loop  aerial. 

10.  Transformer  or   Spark    Coil,  Spark   Gap,  Condenser,   3- 
Contact  Helix,  and  3-Point  Anchor  Gap.     Highly  recommended 
for  loop  aerials. 

11.  Transformer    or    Spark     Coil,    Spark    Gap,    Condenser, 
Oscillation    Transformer.     The    most    practical     and    popular 
circuit    known. 

12.  Transformer,  Spark  Gap,  three  or  more  Condensers,  three 
or    more   Oscillation   Transformers.     A   Multiple  Transmitting 
Circuit.     For  use  with  very  high  power. 

The  best  circuits  for  commercial  and  long  distance  work. 


APPENDIX 


151 


T       AERIAL 


LOOP 


VERTICAL 
SERIAL 


LOOP 


UMBRELLA 
AERIAL 


L      ACR  I  A  L 


V      AERIAL 


STRAIGHT 


LO  OP 


FAN     AERIAL 


152 


APPENDIX 


6 
Q 


— n 


0 
9 


— U 


U 


APPENDIX 


153 


— n 


o- 


-u 
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"G 

Q 


— -n 


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154 


APPENDIX 


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APPENDIX  155 

RECEIVING  CIRCUITS.    I 

SINGLE   SLIDE  TUNING  COILS 

1.  Tuning  Coil,  Detector,  and  Phones.     Simplest  circuit. 

2.  Tuning   Coil,  Fixed    Condenser,  Variable  Condenser,  De- 
tector, and  Phones.     A  simple  tuned  circuit. 

3.  Tuning  Coil,  Fixed  Condenser,  Detector,  and  Phones.    A 
practical  circuit,  but  subject  to  interference. 

4.  Tuning    Coil,    Fixed    Condenser,    Detector,    and    Phones. 
Practical  circuit  for  the  beginner.     Fairly  selective. 

RECEIVING  CIRCUITS.     II 

DOUBLE   SLIDE   TUNING   COILS 

5.  Tuning  Coil,  Fixed    and  Variable   Condensers,  Detector, 
and  Phones. 

6.  Tuning  Coil,  Variable  and  Fixed  Condenser,  Detector,  and 
Phones.     A  practical  circuit,  but  subject  to  interference. 

7.  Tuning  Coil,   Fixed  and  Variable   Condensers,   Detector, 
and  Phones.     A  selective  circuit. 

8.  Tuning   Coil,  Fixed   and  Variable  Condensers,  Detector, 
and  Phones.     The  most  selective  2-slide  circuit.     Will  overcome 
arc-light  interference  to  a  measure. 

RECEIVING  CIRCUITS.    Ill 

THREE   SLIDE  TUNING  COILS 

9.  Tuning  Coil,  Fixed  and  Variable  Condensers,  Detector,  and 
Phones.    An  all-around  selective  circuit. 

10.  Tuning  Coil,  Fixed  and  Variable  Condensers,  Detector, 
and  Phones.     Overcomes  arc-light  interference. 

11.  Tuning  Coil,  Fixed  Condenser,  two  Variable  Condensers, 
Detector,  and  Phones.     Very  selective  circuit  for  overcoming 
static  and  arc-light  interference. 


156  APPENDIX 

12.  Tuning  Coil,  Fixed  and  Variable  Condensers,  Detector, 
and  Phones.     The  best  3-Slide  circuit  known.     Has  auxiliary 
loose  coupling,  which  has  an  effect  similar  to  an  oscillation  trans- 
former.    Good  for  overcoming  all  kinds  of  interference. 

RECEIVING  CIRCUITS.    IV 

SPLIT   AERIAL   CIRCUITS 

13.  Two  Single  Slide  Tuning    Coils,  two    Fixed  Condensers, 
Detector,  and  Phones.     Simple  interference  preventer. 

14.  Two  Double  Slide  Tuning   Coils,  Fixed  Condenser,  De- 
tector, and   Phones.     Adapted    to  overcome   the   humming   of 
motor  and  power  wires. 

15.  One  Single  and  one  3-Slide  Tuning  Coil,  Fixed  Condenser, 
two  Variable   Condensers,    Detector,    and   Phones.     Will  over- 
come interference  from  near-by  stations. 

16.  Two  Single  Slide  Tuning  Coils,  two  Fixed  and  one  Variable 
Condenser,  Detector,  and  Phones.     An  all-around  interference  pre- 
venter, and  a  very  popular  circuit. 

Circuits  specially   for  overcoming   different   forms  of  inter- 
ference. 

RECEIVING  CIRCUITS.    V 

LOOP   AERIALS 

17.  Double  Slide  Tuning  Coil,  Fixed  Condenser,  Detector,  and 
Phones.     A  simple  loop  circuit. 

18.  Double  Slide  Tuning  Coil,  Fixed  and  Variable  Condensers, 
Detector,  and  Phones.     A  practical  circuit  for  all-around  work. 

19.  Two  Double  Slide  Tuning  Coils,  two  Variable  Condensers, 
Detector,  and  Phones.     For  overcoming  interference. 

20.  One  Single  and  one  Double  Slide  Tuning  Coil,  Fixed  and 
two  Variable  Condensers,  Detector,  and  Phones.     A  very  selective 
loop  circuit.     The  best  and  most  popular  form. 

Loop  aerials  somewhat  less  practical  than  the   straight-away 
forms  for  general  work. 


APPENDIX  157 

RECEIVING  CIRCUITS.    VI 

LOOSE  COUPLED  TUNING  COILS 

21.  Loose  Coupled  Tuning  Coil,  Fixed  Condenser,  Detector, 
and  Phones.     Simplest  circuit. 

22.  Loose  Coupled  Tuning  Coil,  Fixed  and  Variable  Conden- 
sers, Detector,  and  Phones.   An  extremely  selective  and  sensitive 
circuit.     The  most  popular  circuit. 

23.  Loose  Coupled  Tuning  Coil,  Loading  Coil,  Fixed  and  two 
Variable  Condensers,  Detector,  and  Phones.     The  addition  of 
extra  inductance  in  the  circuit,  when  receiving  very  long  waves. 
By  adding  the  second  Variable  Condenser  alone,  short  waves 
may  be  tuned  in. 

24.  Loose  Coupled  Tuning  Coil,  Single  Slide  Tuning   Coil, 
Fixed  and  three  Variable   Condensers,   Detector,  and  Phones. 
This  is  for  use  in  overcoming  extreme  interference  and  the  hum- 
ming from  high-tension  lines. 

The  best  and  most  practical  circuits  for  commercial  and  pro- 
fessional use. 

RECEIVING  CIRCUITS.     VII 

25.  Loose   Coupled   Tuning   Coil,    Fixed  and   two   Variable 
Condensers,  Detector,  and  Phones.     For  loop  aerials. 

26.  Loose  Coupled  and  Loading  Coil,  Fixed  and  two  Variable 
Condensers,  Detector,  and  Phones.     For  loop  aerials.     A  prac- 
tical circuit. 

27.  Two  Loose  Coupled  Tuning  Coils,  Loading  Coil,  Fixed 
and  three  Variable  Condensers,  Detector,  and  Phones.   A  weeding- 
out  circuit.     Extremely  selective,  and  excellent  for  overcoming 
all  kinds  of  interference. 

28.  Three  Loose  Coupled  Tuning  Coils,  Loading  Coil,  Fixed 
and    four  Variable    Condensers,    Detector,    and    Phones.    The 
tertiary  weeding-out  circuit.     Its  selectivity  is  wonderful,  but 
it  is  not  wholly  practical,  a  slight  amount  of  energy  being  lost 
with  the  addition  of  each  additional  loose  coupled  tuning  coil. 


158 


APPENDIX 


APPENDIX 


159 


1 


160 


APPENDIX 


\1J 


\\ 


10 


APPENDIX 


161 


IS" 


16 


162 


APPENDIX 


APPENDIX 


163 


164 


APPENDIX 


25- 


2.  8 


APPENDIX  165 

COMPLETE  SETS.     I 

1.  Transmitting  Apparatus:   Spark   Coil,    Spark   Gap,    Con- 
denser, and  a  i,  2,  or  3  Clip  Helix.     For  use  with  batteries  and 
telegraph  key. 

Receiving  Apparatus:  i,  2,  or  3  Slide  Tuning  Coil,  Fixed  Con- 
denser, Detector,  and  Phones.  A  Variable  Condenser  may  be 
added. 

Switch  between  Sending  and  Receiving:  S.P.D.T. 

A  beginner's  set. 

COMPLETE  SETS.    II 

2.  Transmitting    Apparatus:    Spark    Coil    or    Transformer, 
Spark  Gap,  Condenser,  3  or  4  Contact  Helix.     To  be  run  from 
battery  or  power,  key  with   durable  contacts   and   adjustable 
resistance. 

Receiving  Apparatus:  Loose  Coupled  Tuning  Coil,  Fixed  and 
Variable  Condenser,  Detector,  and  Phones. 

Switch  between  Sending  and  Receiving:  D.P.D.T. 
A  practical  set. 

COMPLETE  SETS.    Ill 

3.  Transmitting  Apparatus:   Transformer   Spark   Gap,   Con- 
denser, Sending  Oscillation  Transformer,  two  protective  devices 
for  the  line  and  transformer,  Rheostat  or  Reactance  Regulator, 
a  Key  with  heavy  contacts.     A  Condenser  across  the  key  points 
to  prevent  formation  of  arc  between  them. 

Receiving  Apparatus:  Loose  Coupled  Tuning  Coil,  Fixed  and 
Variable  Condensers,  Detector,  and  Phones. 

Breaking-in  System:  Relay  with  single  contact,  protective 
Spark  Gap,  and  Batteries  for  relay  circuit. 

Aerial  Switch  of  100  amperes. 


166  APPENDIX 

COMPLETE  SETS.    IV 

TWO  TO  FIVE   KILOWATT 

4.  Transmitting  Apparatus:  Transformer,  Spark  Gap,  Con- 
denser, Oscillation  Transformer,  three  protective  devices  for  the 
transformer,  the  switchboard,  and  for  the  dynamo,  a  Reactance 
Regulator,  key  with  heavy  contacts  with  condenser. 

Receiving  Apparatus:  Loose  Coupled  Tuning  Coil,  Loading 
Coil,  Fixed  and  two  Variable  Condensers,  Detector  with  potenti- 
ometer, Battery  and  Switch,  and  Phones. 

Breaking-in  System:  Aerial  Relay  with  two  contacts,  two 
protective  Spark  Gaps,  Relay  with  six  contacts  for  protecting 
the  detector,  and  Batteries. 

Switch  of  100  amperes. 


APPENDIX 


167 


o 


S-F-D-T 


168 


APPENDIX 


APPENDIX 


169 


170 


APPENDIX 


TABLE  OF    SENDING    AND    RECEIVING  DISTANCES 

In  wireless  telegraphy  the  one  thing  unknown  is  the  distance 
covered  by  our  instruments.  In  line  telegraphy  the  distance 
is  regulated  by  the  length  of  wire.  Only  the  limitations  of  power 
limit  our  transmitting  possibilities  in  wireless;  and  the  degree 
of  sensitiveness  shown  in  our  receiving  instruments  regulates 
the  distances  of  the  stations  whose  signals  we  can  catch.  Every 
experimenter,  indeed  every  operator,  wants  to  know  what  those 
distances  are:  how  far  do  his  signals  carry,  and  how  far  away  is 
the  most  distant  station  whose  call  he  can  receive. 

Every  instrument  in  the  set,  its  separate  quality,  influences 
this  distance,  and  the  result  must  depend  somewhat  upon  per- 
sonal judgment.  However,  the  author  has  made  tables  which 
may  be  used  roughly  to  indicate  the  range  of  stations  consisting 
of  different  sorts  of  apparatus.  They  will  be  found  pretty 
nearly  adequate  in  all  cases,  if  the  instruments  are  carefully 
judged. 

A  TABLE  OF  RECEIVING  DISTANCES 
AERIALS 

Position 

Hill  (within  10  miles  of  seacoast) i 

"  (30  miles  or  more  inland) f 

Low  land  (sea,  coast) ^ 

"  "  (clear  space,  inland) f 

"  "  (city  or  forest) i 


Type  and  Value 

Vertical  Height 

Horizontal  Length 

T  L  V 

Umbrella,  Fan 
Vertical 

i  in  feet 

i  «     « 

*  "  " 

t*&  in  feet 
\  spread,  in  feet 

f  k 


APPENDIX 


171 


CIRCUIT  VALUES 
| 

Circuits  in  back  of  book  as  standards 
Number 

i,  2,  3,  13- •• £ 

4,  5>  14,  15 •  t 

6,  16,  17,  18 f 

7,  8,  9,  19 TV 

10,  II,  12,  20 f 

25, 26, 27, 28 & 

21,   22,   23,    24 I 

DETECTORS  AND  TELEPHONE  RECEIVERS 
DOUBLE  POLE,  ALL  COPPER  WOUND 


Resistance 
per  Pair 

Perikon- 
Elektra 

Perikon 
with  Bat. 

Perikon 
No  Bat. 

Pyron  or 
Perron 

Electro- 
lytic 

Silicon 

80 

20 

12 

1O 

IO 

8 

6 

250 

22 

13 

II 

II 

9 

7 

500 

23 

14 

12 

II 

IO 

8 

750 

24 

14 

13 

12 

II 

8 

IOOO 

24 

15 

14 

12 

II 

9 

1500 

25 

15 

14 

13 

12 

9 

2000 

24 

15 

14 

12 

II 

9 

3000 

24 

16 

15 

12 

10 

10 

Explanation  of  Table.  Select  conditions  of  the  set 
in  question,  and  multiply  their  values  together  to  find 
total  receiving  distance  of  station.  These  distances 
may  be  nearly  doubled  for  special  atmospheric  condi- 
tions, and  with  a  good  operator.  Good  between  8  p.  M. 
and  4  A.  M.  Subtract  20%  for  day  use. 


172 


APPENDIX 


Example 

Aerial,  Length  180       TV  x  180=18 

"      Height  90        Jxgo  =30 

Value  for  Aerial         48 

Position,  Low,  Coast  ^ 

Circuit,  No.  21  i 

Detector,  Pyron,  Phones  1500  ohms      13 

48  x  y9^  x  i  x  13  =  560  miles 

SIZES  OF  AERIAL  WIRES 


Material 

Smallest 
Size 

Largest 
Size 

Kind 

Copper  . 

14. 

8 

Stranded  or  solid 

Phosphor  bronze  

12 

6 

Stranded  or  solid 

Aluminum  

12 

6 

Solid 

Iron  (umbrella  type)  .  . 

IO 

4 

Solid 

AERIAL    INSULATION 

Power  Size  of  Insulators 

i  and  2  Inch  spark  coils  ..............  Porcelain  cleats  or  spools 

kw.  set     ..........................  2  inch  strain  insulators 


2 

6 

6 

18 

.  .18 


A  TABLE  OF  SENDING  DISTANCES 


AERIALS 

Must  have  two  or  more  strands 
i.   Position 

On  seacoast,  high  land,  clear  space I 

On  coast,  low  land '   >••§.• 


APPENDIX  173 

High  land,  inland i 

Low  land,  city  or  forest i 

2.  Size 

Height  of  aerial  over  100  feet i 

60-100  foot  aerial t 

40-60      "        "    J 

30-40      "        "    i 

CIRCUIT 

3.  Numbers  from  chapter  on  transmitting  diagrams 

11-12 i 

5,7,8 | 

6,  9,  10 i 

1,2,3,4 i 

WAVE  LENGTH 
Not  under  400  metres 
POWER 


Transformers 

5  kw  

600 

4  

480 

3    

420 

2!    

370 

2     

300 

l£  

290 

I     .  .  

240 

£ 

2IO 

^                                                        

180 

\                                                                       

120 

i     

75 

Battery-operated  Spark  Coils 

50   watts  (4  inch   spark   coil)  

40 

2.;       "      (2     "         "       "    )  

25 

15       "     (i     "         "        "  )  

12 

10          "        (i       "              "           "     )   

8 

174 


APPENDIX 


Explanation  of  Table.  Select  the  conditions  of  the 
set  in  question,  and  multiply  together  to  obtain  send- 
ing distance  of  the  station.  These  distances  may 
be  nearly  doubled  when  atmospheric  conditions  are 
especially  favorable.  A  good  operator  will  also  im- 
prove the  distance  somewhat. 

Example.     A  station  on  the  coast,  but  low  land;  a  loo-foot 
aerial;  a  good  circuit,  using  a  helix;  a  one  i-kw.  transformer. 
123       4  Result,  Distance 
|  x  i  x  f  x  240=  135  miles 

COMPARISON    OF    COPPER    AND    ALUMINUM 


Copper 

Aluminum 

Specific  gravity    
Conductivity  

8.93 

IOO 

2.68 
63 

Area     ....         ... 

IOO 

48 

Diameter 

IOO 

126  04 

This  shows  that  aluminum  has  63%  as  great  con- 
ductivity and  48%  of  the  weight  of  copper;  that  for 
wire  of  equivalent  conductivity  it  has  a  cross  section 
60%  greater  and  a  diameter  26.4%  greater  than 
copper. 

It  will  be  noted  from  the  relative  diameters  that  an 
aluminum  wire  of  equal  conductivity  with  a  copper 
wire  will  be  almost  exactly  two  sizes  larger  by  the 
B  &  S  Gauge. 

Weight  to  weight,  therefore,  the  conductivity  of 
aluminum  is  greater  than  that  of  copper  by  315% 


Table  of  Dimensions  and  Resistances  of  Pure 
Copper  Wire.* 

KEVISED. 


No. 
B. 

& 
S. 

Kesistance  at  75°F. 

bs  p.  1000 
ft.  ins'd 
H.B.&H. 
ine  wire. 

Feet   pei 
Ib.  ins'd 
H.B.&H. 
ine  wire. 

R 

ohms  per 
1000  feet. 

Ohms 
per 
mile. 

Feet 
per 
ohm. 

Ohms 
per 
pound. 

4-0 
3-0 
00 
0 

.04904 
.06184 
.07797 
.09827 

.25891 
.32649 
.41168 
.51885 

20392.9 
16172.1 
12825.4 
10176.4 

.00007653 
.00012169 
.00019438 
.00030734 

800 
666 
500 
363 

1.25 
1.50 
200 
2.75 

2 
3 
4 
5 

.12398 
.15633 
.19714 
.24858 
.31346 

.65460 
.82543 
1.04090 
1.31248 
1.65507 

8066.0 
6396.7 
5072.5 
4022.9 
3190.2 

.00048920 
.00077784 
.0012370 
.0019666 
.0031273 

313 
•    250 
200 
144 
125 

3.20 
4.00   ' 
5.00 
6.9 
8.0 

6 
7 
8 
9 
10 

.39528 
.49845 
.62849 
.79242 
.99948 

2.08706 
2.63184 
3.31843 
4.18400 
5.27726 

2529.9 
2006.2 
1591.1 
1262.0 
1000.5 

.0049728 
.0079078 
.0125719 
.0199853 
.0317946 

105 
87 
69 

50 

9.5 
11.5 
14.5 

20.0 

11 
12 
13 
14 
15 

~w 

17 
18 
19 
20 

1.2602 
1.5890 
2.0037 
2.5266 
3.1860 

6.65357 
8.39001 
10.5798 
13.3405 
16.8223 

793.56 
629.32 
499.06 
395.79 
313.87 

.0505413 
.0803641 
.127788 
.203180 
.323079 

31 

22 

32.0 
45.0  ' 

4.0176 
5.0660 
-       6.3880 
8.0555 
10.1584 

21.2130 
26.7485 
33.7285 
42.5329 
53.6362 

248.90 
197.39 
156.54 
124.14 
98.44 

.513737 
.816839 
1.298764 
2.065312 
3.284374 

14 
11 

70.0 
90.0 

21 

22 
23 
24 
25 

12.8088 
16.1504 
20.3674 
25.6830 
32.3833 

67.6302 
85.2743 
107.540 
135.606 
170.984 

78.07 
61.92 
49.10 
38.94 
30.88 

5.221775 
8.301819 
13.20312 
20.99405 
33.37780 

26 

27 
28 
29 
30 

40.8377 
51.4952 
64.9344 
81.8827 
103.245 

215.623 
271.895 
342.854 
432.341 
545.133 

24.4y 
19.42 
15.40 
12.21 
9.686 

53.07946 
84.39916 
134.2  '05 
213.3973 
339.2673 

31 
32 
33 
34 
35 
36 
37 
38 
39 
40 

130.176 
164.174 
207.000 
261.099 
329.225 

687.327 
866.837 
1092.96 
1378.60 
1738.31 

7.682 
6.091 
4.831 
3.830 
3.037 

539.3404 

857.8498 
1363.786 
2169.776 
3449.770 

415.047 
523.278 
660.011 
832.228 
1049.718 

2191.45 
2762.91 
3484.86 
4394.16 
5542.51 

2.409 
1.911 
1.515 
1.202 
.9526 

5482.766 
8715.030 
13864.51 
22043.92 
35071.11 

mile  pure  copper  wire  1-16  in.  diam.=13.59  ohms  at  15.5°C.  or  59.9°F. 


Table  of  Dimensions  and  Resistances  of  Pure 
Copper   Wire.* 


No. 
B.  &S. 

Diam. 
Mils. 

Area. 

W'gt&  Length.   Sp.gr.  8.9 

Circular 
Mils. 

Square 
Inches. 

Lbs. 
per 
1000  ft. 

Pounds 
per 
mile. 

Feet 
per 
pound. 

0000 
000 
00 
0 

460.000 
409.640 
364.800 
324.950 

211600.0 
167805.0 
133079.0 
105592.5 

166190.2 
131793.7 
104520.0 
82932.2 

640.73 
508.12 
402.97 
319.74 

3383.04 
2682.85 
2127.66 
1688.20 

1.56 
1.97 
2.48 
3.13 

1 

2 
3 
4 
5 

289.300 
257.630 
229.420 
204.310 
181.940 

83694.5 
66373.2 
52633.5 
41742.6 
33192.2 

65733.5 
52129.4 
41338.3 
32784.5 
25998.4 

253.43 
200.98 
159.38 
126.40 
100.23 

1338.10 
1061.17 
841.50 
667.38 
529.23 

3.95 
4.98 
6.28 
7.91 
9.98 

6 

7 
8 
9 
10 

162.020 
144.280 
128.490 
114.430 
101.890 

26250.5 
20816.7 
16509.7 
13094.2 
10381.6 
8234.11 
6529.94 
5178.39 
4106.76 
3256.76 

20617.1 
16349.4 
12966.7 
10284.2 
8153.67 

79.49 
63.03 
49.99 
39.65 
31.44 

419.69 
332.82 
263.96 
209.35 
165.98 

12.58 
15.86 
20.00 
25.22 
31.81 

11 
12 
13 
14 
15 

90.742 
80.808 
71.961 
64.084 
57.068 

6467.06 
5128.60 
4067.09 
3225.44 
2557.85 

24.93 
19.77 
15.68 
12.44 
9.86 

131.65 
104.40 
82.792 
65.658 
52.069 

40.11 

50.58 
63.78 
80.42 
101.40 

16 

17 
18 
19 
20 

50.820 
45.257 
40.303 
35.890 
31.961 

2582.67 
2048.20 
1624.33 
1288.09 
1021.44 

2028.43 
1608.65 
1275.75 
1011.66 
802.24 

7.82 
6.20 
4.92 
3.90 
3.09 

41.292 
32.746 
25.970 
20594 
16.331 

127.87 
161.24 
203.31 
256.89 
323.32 

21 
22 
23 
24 
25 

28.462 
25.347 
22.571 
20.100 
17.900 

810.09 
642.47 
509.45 
404.01 
320.41 

636.24 
504.60 
400.12 
317.31 
251.65 

2.45 
1.95 
1.54 
1.22 
.97 

12.952 
10.272 
8.1450 
6.4593 
5.1227 
41)623" 
3.2215 
2.5548 
2.0260 
1.6068 

407.67 
514.03 
648.25 
817.43 
1030.71 

26 
27 
28 
29 
30 

15.940 
14.195 
12.641 
11.257 
10.025 

254.08 
201.50 
159.80 
126.72 
100.50 

199.56 
158.26 
125.50 
99.526 
78.933 

.77 
.61 
.48 
.38 
.30 

1299.77 
1638.97 
2066.71 
2606.13 
3286.04 

31 
32 
33 
34 
35 

8.928 
7.950 
7.080 
6.304 
5.614 

79.71 
63.20 
50.13 
39.74 
31.52 

62.603 
49.639 
39.369 
31.212 
24.753 

.24 
.19 
.15 
.12 
.10 

1.2744 
1.0105 
.8014 
.6354 
.5039 

4143.18 
5225.26 
6588.33 
8310.17 
10478.46 

36 
37 
38 
39 

40 

5.000 
4.453 
3.965 
3.531 
3.144 

25.00 
19.83 
15.72 
12.47 

9.88 

19.635 
15.574 
12.347 
9.7923 

7.7365 

.08 
.06 
.05 
.04 
.03 

.3997 
.3170 
.2513 
.1993 
.1580 

13209.98 
16654.70 
21006.60 
26427.83 
33410.05 

"1  mile  pure  copper  wire  1-16  in.  diam.=13.59  ohms  at  15.5°C  or  59.9°F. 


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"H-C" 

Wireless 
Operator's 

Head 
Receivers 

IN  wireless  telephone  receivers  the  important  points  to  be  considered 
are,  first,  their  sensitiveness;  second,  the  degree  of  comfort  with 
which  they  can  be  worn;  third,  their  permanence  of  adjustment 
and  construction. 

There  are  many  points  in  the  design  of  receivers  which  affect  their 
sensitiveness.  The  coils  must  be  wound  so  as  to  give  the  greatest 
possible  number  of  turns  with  the  least  resistance.  Many  people  assume 
that  high  resistance  means  great  sensitiveness.  This  is  not  necessarily 
the  case.  The  most  efficient  winding  is  the  one  having  the  greatest 
number  of  turns  of  wire  nearest  the  cores  for  a  given  ohmic  resistance. 
It  would  be  possible,  for  instance,  to  wind  the  cores  with  German  silver 
wire  and  get  a  very  high  resistance,  but  it  would  give  a  very  poor  receiver. 
The  amount  of  iron  in  the  cores  and  the  quality  of  the  iron  are  also 
important  factors. 

The  diameter  and  thickness  of  the  diaphragm  and  the  quality  of  the 
iron  from  which  it  is  made  also  greatly  affect  the  sensitiveness. 

Another  feature  that  must  be  watched  is  the  strength  of  the  perma- 
nent magnets.  These  must  be  just  the  right  strength  to  give  the  best 
results  with  the  cores  and  diaphragms  with  which  they  are  used.  Per- 
manence of  adjustment  can  be  secured  only  by  mounting  all  the  parts 
mentioned  on  some  material  which  will  be  unaffected  by  heat  or  moisture. 

H-C  Head  Receivers  have  been  designed  with  all  of  the  above  points 
in  view.  The  windings  are  all  made  with  silk  covered  copper  wire.  The 
magnets  are  made  from  a  special  quality  of  steel  and  are  of  the  proper 
strength  to  give  best  results  with  the  diaphragms  used.  The  spools  and 
magnets  are  mounted  in  a  metal  cup  which  supports  the  diaphragm. 
The  cores  are  ground  to  a  proper  height  so  that  the  adjustment  is  per- 
manent. The  metal  cup  is  enclosed  in  a  hard  rubber  shell.  The  two 
receivers  are  mounted  on  an  adjustable  leather  covered  head  band. 
There  are  no  nuts  or  screws  to  work  loose  on  this  band,  and  nothing  to 
catch  the  hair.  Large  pneumatic  rubber  cushions  are  provided  with 
each  set,  which  not  only  shut  out  extraneous  noises  but  also  make  the 
set  more  comfortable.  These  cushions  are  readily  detachable.  A  six- 
foot  two  conductor  green  silk  tinsel  cord  is  supplied  with  each  set  also. 

These  sets  may  be  wound  to  resistance  up  to  4,000  ohms. 

HOLTZER-CABOT   ELECTRIC   CO. 

BROOKLINE,   MASS.,  U.  S.  A. 


T 

4 

TRANSMITTING 
SET 


WIRELESS   TELEGRAPH 
APPARATUS 

OF 

ABSOLUTE   RELIABILITY 

FOR 

PRIVATE,  COMMERCIAL  &  GOVERNMENT 
INSTALLATION 

STAMP  FOR  ILLUSTRATED  CATALOGUE 

CLAPP-EASTHAM  CO. 

139  MAIN  STREET       ....       CAMBRIDGE,  MASS. 


CABINET 

TYPE 
RECEIVING 

SET 


IMPROVED  NAVY 


THE  BEST  WIRELESS  RECEIVER  MADE  FOR 
LONG  DISTANCE  WORK 

THE   REASONS 

SENSITIVENESS  ^   SOFT  AND  DISTINCT 

TONE    ^    SAME    PITCH    IN    BOTH 

RECEIVERS  jt  IS  THE  LIGHTEST  AND 

MOST  COMFORTABLE  SET  MADE 

Complete  outfit  weighs  only  10  ounces 

LET  US  PROVE  OUR  CLAIMS  ::  SEND  FOR  A  PAIR  ON  TRIAL 
Send  for  catalogue  and  record  bulletin  F.  D. 

C.  BRANDES         1 1 1  BROADWAY,  NEW  YORK 


SUPPLEMENT 


Wireless  Operators'  Pocket-book 


Information  and  Diagrams 


LEON  W.  BISHOP 


LATEST  CALL  LIST  OF 
WIRELESS  STATIONS 


ALPHABETICALLY    ARRANGED' 


1911 


BUBIER     PUBLISHING     COMPANY 

LYNN,  MASS.,  U.S.A. 


WIRELESS  OPERATORS'  POCKET-BOOK 

OF 

Information  and  Diagrams 

SUPPLEMENT 
LATEST    GALL    LIST    OF     STATIONS 

S.  S.  Roanoke  AQ 

S.  S.  San  Jacinto  AS 

S.  S.  Admiral  Sampson  AS 
Amsterdam  navy-yard  ASD 
U.  S.  Army  transport  Buford 

ATB 
U.  S.  Army  transport  Dix 

ATD 
IT.  S.  Army  transport  Sumner 

ATH 

U.  S.  Army  transport  Kilpat- 
rick  ATK 

U.  S  .Army  transport  Logan 

ATL 

U.  S.  Army  transport  Sher- 
man ATR 
U.  S.  Army  transport  Sheri- 
dan ATS 
U.  S.  Army  transport  Thomas 

ATU 

S.  S.  Dolphin 
Chatham,  Mass. 
S.  S.  Seward 
S.  S.  Olympia 
S.  S.  Kansas  City 
Atlantic  City,  N.J. 
S.  S.  Geo.  W.  Elder 
S.  S.  Brazos 

Avalon,  Catalina  Island,  Cal. 
A2 

Tug  Tyee  A3 

Baltimore,  Md.  (American 

Building)  B 

Bocas  del  Toro,  Panama     B 


Isles  of  Shoals,  N.H.  A 

S.  S.  Alabama  AB 

S.  S.  Sabine  AB 

S.  S.  Chicago  AB 

S.  S.  Aberdeen  ABD 

S.  S.  Concho  AC 

S.  S.  Denver  AD 

S.  S.  Victoria  AD 

Amsterdam,  Holland  ADM 

S.  S.  Colorado  AF 

S.  S.  Rio  Grande  AG 

S.  S.  Yucatan  AG 

S.  S.  Nueces  AH 

S.  S.  Pennsylvania  AH 

S.  S.  Alamo  AJ 

German  pilot  steamer  Jade 

AJA 

S.  S.  San  Marcos  AK 

S.  S.  Santa  Clara  AK 

S.  S.  Loftus  Cuddy  AL 

Algiers,  Algeria  ALG 

Almeria,  Spain  ALM 

S.  S.  America  AM 

S.  S.  Comal  AM 

S.  S.  Riverside  AM 
Kamalo,   Molokai,   Hawaiian 

Islands  AM 

S.  S.  Northwestern  AN 

Antivari,  Montenegro  AN 

S.  S.  Minda  AND 

•S.  S.  Ohio  AO 

S.  S.  Lampasas  AP 
S.  S.  City  of  Benton  Harbor 
AQ 


AU 
AU 
AV 
AW 
AX 
AX 
AY 
AZ 


WIRELESS  OPERATORS'   POCKETBOOK 


S.  S.  Bermudian  BA 

Buenos  Aires,  Argentine  Re- 
public BA 
Batavia,  Dutch  East  Indies 

BA 

Abo,  Russia  BAG 

S.  S.  Batavier  IV  BBF 

S.  S.  Batavier  II  BBS 

S.  S.  Batavier  III  BBT 

S.  S.  Batavier  V  BBV 

S.  S.  Virginia  BC 

S.  S.  W.  S.  Porter  BD 

S.  S.  Trinidad  BD 

New  York,  N.Y.  BD 

Buffalo,  N.Y.  (News  Build- 
ing) BF 
Philadelphia,  Pa.  BF 
Bridgeport,  Conn.  BG 
S.  S.  Iroquois  BG 
Helsingfors.  Finland  BGF 
Quincy,  Mass.  BH 
S.  S.  Chippewa  BH 
Benton  Harbor,  Mich.  BH 
Blaavands  Huk,  Denmark 

BH 

S.  S.  Indianapolis  Bl 

S.  S.John  J.  Barium  BJ 

Leckte,  Russia  BLH 

Libau,  Russia  BLW 

S.  S.  Nyack  BM 

S.  S.  Boston  BX 

S.  S.  Rosecrans  BX 

Nikolaistadt,  Russia     BNCh 
S.  S.  Nann  Smith  BO 

Brant,  Rock  Mass.  BO 

S.  S.  Hermosa  BP 

Preste,  Russia  BPS 

S.  S.  Bruce  BR 

S.  S.  Thomas  Barium        BR 
Britz,  Germany  BR 

Overtoom,  Holland      BRBR 
Reval,  Russia  BRW 


Philadelphia,  Pa.  ( Belle vue- 
Stratford)  BS 

Washington,  B.C.,  Bureau  of 
Standards  BS 

U.  S  .  Army  cableship  Burn- 
side  BS 
Sevastapol,  Russia  BSP 
S.  S.  Nyades  BT 
Butt  of  Lewis,  Scotland  BTL 
S.  S.  Rupert  City  BU 
S.  S.  Cabrillo  BV 
S.  S.  Alliance  BW 
Vladivostok,  Siberia  BWT 
S.  S.  City  of  South  Haven 

BX 

Shoeburyness,  England     BY 
Babylonia,  Brazil  BYN 

Bombay,  India  BYR 

Bessemer  Barge  No.  2        B2 
Tug  Goliah  B3 

Camaguey,  Cuba  C 

S.  S.  City  of  Alpena  CA 

S.  S.  Coamo  CA 

S.  S.  Priscilla  CA 

Cambridge,  England  CA 

Saginaw,  Mich.  CAN 

S.  S.  Ashtabula  CAR 

S.  S.  Regele  Carol  I         CAR 
S.S.Carolina  CB 

Buffalo,  N.Y.  CB 

Boca  del  Colorado,  Costa  Rica 
CB 

Cheribon.  Dutch  East  Indies 
CB 

S.  S.  Sierra  CBJ 

S.  S.  City  of  Cleveland        CC 
S.  S.  City  of  Detroit  CD 

Duluth,  Minn.  CD 

Olifden,  Ireland  CDN 

Detroit,  Mich.  CF 

Chicago,  111  CG 

Cape  May,  N.J.  CG 


SUPPLEMENT 


S.  S.  City  of  St.  Ignace      CG 
Charlottenburg,  Germany 

CG 

S.  S.  Quadra  CGS 

Port  Huron,  Mich.  CH 

San  Franciso,  Cal.  (Chronicle 

CH 

Chamartin,  Spain  CH 

S.  S.  Harmonic  CHA 

S.  S.  Huronic  CHN 

Erie,  Pa.  CI 

Sault  Ste.  Marie,  Mich.       CJ 
S.  S.  San  Juan  CJ 

S.  S.  Juanita  CJA 

Detroit,  Mich.  (Detroit 

Journal)  CJL 

S.  S.  Charlois  CLS 

Calumet,  Mich.  CM 

Milwaukee,  Wis.  CM 

Buenos  Aires,  Argentine  Re- 
public CM 
S.  S.  Hugh  Kennedy  CMA 
S.  S.  Jos.  Sellewood  CMB 
S.  S.  S.  M.  Clement  CMD 
S.  S.  Pendenis  White  CMF 
S.  S.  Moses  Taylor  CMG 
S.  S.  James  Gayley  CMH 
S.  S.  W.  H.  Gratwick  CMI 
S.  S.  J.  J,  Albright  CMJ 
S.  S.  Walter  Scranton  CMK 
S.  S.  E.  A.  S.  Clarke  CMN 
S  S.  Wm.  E.  Reis  CMP 
S.  S.  N.  A.  Hanna  CMQ 
S.  S.  H.  S.Houlden  CMR 
S.  S.  Lagonda  CMS 
S.  S.  J.  J.  Me  Williams  CMU 
S.  S.  Major  CMV 
S.  S.  Robt.  L.  Fryer  CMW 
Bishop,  Boston,  Mass.  CN 
Cleveland,  Ohio  CN 
Ashtabula,  Ohio  CO 
Cayo  Criso,  Cuba  CO 


Coruna,  Italy  CO 

Marion,  Mass.  CON 

Corvo,  Azores  COR 

S.  S.  Ponce  CP 

Port  Arthur,  Ontario  CPA 
S.  S.  Princess  Charlotte   CPC 

S.  S.  Princess  May  CPM 

S.  S.  Princess  Royal  CPR 

Tug  Tees  CPT 

S.  S.  Princess  Victoria  CPV 

Marquette,  Mich.  CQ 

S.  S.  City  of  Erie  CR 

S.  S.  Senaca  CS 

S.  S.  Eastern  States  CS 

St.  Thomas,  Ontario  CST 

S.  S.  Canada  CT 

Toledo,  Ohio  CT 

S.  S.  Tionesta  CTA 

S.  S.  City  of  Buffalo  CU 

S.  S.  Commonwealth  CW 

S.  S.  Western  States  CW 

Detroit,  Mich.  CW 

S.  S.  St.  Croix  CX 

Cleveland,  Ohio  CX 

Bay  City,  Mich.  CY 

Seattle,  Wash.  (Hotel  Perry) 
DA 

Santa  Clara,  Cuba  DA 

S.  S.  Philadelphia  DA 

S.  S.  Admiral  DAA 
S.  S.  Augustus  B.  Wolvin 

DAB 

S.  S.  Burgomaster  DAB 

S.  S.  Dacia  DAC 

S.  S.  Field  Marshal  DAF 

S.  S.  Adeline  DAH 

S.  S.  Anni  DAI 

S.  S.  Kronprinz  DAK 

S.  S.  James  H.  Hoyt  DAM 

S.  S.  Frank  H.  Peavey  DAN 

S.  S.  Neubau  DAN 

S.  S.  Prinz  Regent  DAP 


WIRELESS  OPERATORS'   POCKET  BOOK 


S.  S.  Adolf  Woennann  DAW 
S.  S.  Prinzessin  DAZ 

Tacoma,  Wash.  DB 

S.  S.  Caracas  DB 

American  schooner  Dorothy 
B.  Barrett  DBB 

S.  S.  Birkenfels  DBB 

Durban,  Hatal  DBN 

S.  S.  Bremen  DBR 

S.  S.  Bulow  DBW 

Washington,   D.C.    (Eighth 

and  Water  streets)         DC 
S.  S.  Iowa  DC 

S.  S.  Cap  Arcona  DCA 

S.  S.  Cap  Blanco  DCB 

S  S.  Cap  Verde  DCE 

S.  S.  Cap  Frio  DCF 

S.  S.  Tietgen  DCF 

S.  S.  Clare  DCH 

S.  S.  Kronprinzessin   Cecile 

DCI 

S.  S.  Clara  Blumenfeld    DCL 
S.  S.  Cap  Ortegal  DCO 

S.  S.  Cap  Roca  DCR 

S.  S.  Cap  Vilabo  DCV 

S.  S.  Kaiserin  Augusta  Vic- 
toria DDA 
S.  S.  Bleucher  DDE 
S.  S.  Cincinnati  DDC 
S.  S.  Bulgaria  DDG 
S.S.Pisa  DDF 
S.  S.  Hamburg  DDK 
S.  S.  President  Lincoln  DDI 
S  S.  Batavia  DDJ 
S.  S.  Deutschland  DDL 
S  S.  Moltke  DDM 
S.  S.  Pennsylvania  DDN 
S.  S.  Prinz  Oscar  DDO 
S.  S.  Patricia  DDP 
S.  S  Pallanza  DDQ 
S.  S.  Amerika  DDR 
S.  S.  President  Grant  DDS 


S.  S.  Pretoria  DDT 

S.  S.  Cleveland  DDV 

S.  S.  Graf  Waldersee  DDW 
S.  S.  Prinz  Adalbert  DDZ 
Pasadena,  Cal.  DE 

S.  S.  Edmund  DEH 

S.  S.  Derfflinger  DER 

S.  S.  Elenore  Woermann 

DEW 

Santa  Barbara,  Cal.      (Hotel 

Potter)  DF 

Vancouver,  British  Columbia 

DF 

S.  S.  Furst  Bismarck  DFB 
S.  S.  Fred.  B.  Wells  DFB 
S.  S.  Fritz  DFH 

Sacramento,  Cal.  DG 

S.  S.  D.  G.  Kerr  DGK 

S  S.  Grosserog  von  Olden- 
burg DGO 
S.  S.  Goeben                   DGN 
S.  S.  Gneisenau               DGU 
S.  S.  Gertrude  Woermann 

DGW 

S.  S.  Kingfisher  DH 

S.  S.  Helene  Blumenfeld 

DHB 

S.  S.  Camerones  DHC 

S.  S.  Heluan  DHE 

S.  S.  Habsburg  DHG 

S.  S.  Mendoza  DHM 

S.  S.  Hohenstauffen  DHN 
S.  S.  Frank  T.  Heffelinger 

DHN 

S.  S.  Hellig  Olav  DHO 

S.  S.  Presidente  de  Mintre 

DHP 
S.  S.  Presidente'Quintana 

DHQ 

S.  S.  Holger  DHR 

S.  S.  Kingsway  DI 

S.  S.  Imperator  DIR 


SUPPLEMENT 


San  Pedro,  Cal.  DJ 

S.  S.  James  C.  Wallace  DJC 
S.  S.  James  H.  Reed  DJR 
Everett,  Wash.  DK 

S.  S.  Kronprinzessin 

Cecile  DKA 

S.  S.  Berlin  DKB 

Ikeda  Head,  Wash.  DKD 
S  S.  Friedrich  der  Grosse 

DKD 

S.  S.  Princess  Irene  DKE 
S.  S.  Prinz  Friedrich 

August  DKF 

S.  S.  Konig  Friedrich 

August  DKF 

S.  S.  Konig  Wilhelm  II  DKG 
S.  S.  Grosser  Kurfurst  DKG 
S.  S.  Main  DKI 

S.  S.  Neckar  DKK 

S  S.  Konigen  Luise        DKL 
S.  S.  Kaiser  Wilhelm  II  DK 
S.  S.  George  Washington 

DKN 

S.  S.  Konig  Albert  DKO 
S.  S.  Kronprinz  Wilhelm 

DKP 

S.  S.  Rhein  DKR 

S.  S.  Barbarossa  DKS 

S.  S.  Kaiser  Wilhelm  der 

Grosse  DKW 

S.  S.  Princess  Alice  DKZ 
S.  S.  Lutzow  DLO 

S.  S.  Lucile  Woermann  DLW 
Duluth,  Minn.  .  DM 

S.  S.  Meteor  DMR 

S.  S.  Mainz  DMZ 

San  Luis  Obispo,  Cal.  DN 
Drogden,  Denmark  DN 

S.  S.  Nora  DNH 

S.  S.  Moskwa  DOA 

S.  S.  Oscar  second  DOR 

Dieppe,  France  DP 


S.  S.  Prince  Adalbert  DPA 
S.  S.  Prinz  Eitel  Fried- 
rich  DPE 
S.  S.  Prinz  Ludwig  DPL 
S.  S.  Prince  Sigismund  DPS 
S.  S.  Prince  Waldemar  DPW 
Eugene,  Oreg.  DR 
Detroit,  Mich.  DR 
S.  S.  Corcovado  DRC 
S.  S.  Prinz  Regent  Luit- 

pold  DRL 

S.  S.  Roon  DRN 

South  Haven,  Mich.  DS 

Port  Townsend,  Wash  DS 
S.  S.  Scharnhorst  DSA 

S.  S.  Senator  Holthusen  DSH 
S.  S.  Sarnia  DSM 

S.  S.  H.  P.  Bope  DSO 

S.  S.  Senator  Refardt  DSR 
S.  S.  Kleist  DST 

S.  S.  Siberia  DSV 

S.  S.  Seyditz  DSZ 

S.  S.  Titania  DTG 

S.  S.  Admiral  '  DTP 

Wilmington,  Del.  DU 

Juneau,  Alaska  DU 

S.  S.  Geo.  W.  Peavey  DUF 
S.  S.  United  States  DUS 
Chehalis,  Wash.  DV 

Newport,  Oreg.  DW 

S.  S.  Ward  Ames  DWA 

Toledo,  Ohio  (Hotel  Secor) 

DX 

S.  S.  Ypiranga  DYA 

S.  S.Yorck  DYK 

Lansing,  Mich.  DZ 

Portland,  Oreg.  DZ 

S.  S.  Ziethan  DZN 

American  schooner  Pendleton 
Sisters  Dl 

Port  Townsend,  Wash.       D2 


8 


WIRELESS   OPERATORS'   POCKET  BOOK 


S.  S.  Earl  Grey  EG 

S.  S.  El  Norte  EN 

S.  S.  Easton  ES 

Cerritos  de  Sinaloa, 

Mexico  EY 

U.  S.  Army  cable  boat 

Field  FA 

S.  S.  City  of  Columbus      FA 
Malabang,  P.  I.  FA 

Fayal.  Azores  FAL 

Outer  Jade  lightship,  Ger- 
many FAU 
S.  S.  City  of  Atlanta  FB 
Fairbanks,  Alaska  FB 
Borkum  Reef  lightship,  Ger- 
many FBR 
Fort  Andrews,  Mass.  FC 
S.  S.  City  of  Macon  FC 
Fort  Wood,  N.  Y.  FD 
S.  S.  City  of  Memphis  FD 
Nome,  Alaska  FD 
Ferrol,  Spain  FE 
Kotlik,  Alaska  FE 
Elbe  I  lightship,  Ger- 
many FEF 
S.  S.  Naomi  FG 
Fort  Gibbon,  Alaska  FG 
Corregidor  Island,  P.  I.  FH 
Eider  lightship,  Germany 

FIF 

S.  S.  City  of  Augusta          FJ 
Fort  Stevens,  Oreg.  FJ 

S.  S.  City  of  Savannah      FK 
Circle  City,  Alaska  FK 

Fort  Leavenworth,  Kans.  FL 
Flores,  Azores  FLO 

Flekkero,  Norway  FLK 

Fort  St.  Michael,  Alaska   FM 
Fort  Morgan,  Ala.  FM 

Zamboanga,  P.  I.  FM 

Fort  Hancock,  N.  J.  FN 

Flannon,  Isle,  Scotland  FNL 


Fastnet,  Ireland  FNT 

Fort  Monroe,  Va.  FO 

S.  S.  Nacoochee  EP 

Petersburg,  Alaska  FP 

Fort  Egbert,  Alaska  FQ 

U.  S.  Army  Cable  Ship 

Joseph  Henry  FR 

Fort  Omaha,  Nebr.  FS 

Jolo,  P.  I.  FS 

Fort  Totten,  N.  Y.  FT 

Fort  Levett,  Me.  FV 

Villegignon,  Brazil  FVG 
Fort  H.  G.  Wright,  N.Y.  FW 
Wrangell,  Alaska  FW 

Wesser  lightship,  Germany 

S.  S.  City  of  St.  Louis  FX 
Fort  Worden,  Wash.  FX 
S.  S.  City  of  Montgomery  FY 
U.  S.  Artillery  harbor  tug, 

General  R.  B.  Ay  res      FY 
Yacht  Lydonia  FZ 

Fort  Riley,  Kans.  FZ 

S.  S.  City  of  Seattle  GA 

S.  S.  Capt.  A.  F.  Lucas  CB 
Cape  Breton,  Glace  Bay, 

Nova  Scotia  GB 

Bolt  Head,  England  GBA 
S.  S.  Georgia  GC 

Brow  Head,  Ireland  GCK 
Caistor,  England  GCS 

Standard  Oil  barge  91  GD 
Graady  lightship,  Den- 
mark GD 
S.  S.  City  of  Everett  GF 
S.  S.  Falcon  GF 
S.  S.  Maverick  GH 
Grand  Haven,  Mich.  GH 
Gjedser,  Denmark  GJ 
S.  S.  Cottage  City  GK 
Standard  Oil  barge  94  GK 
Karlskrona,  Sweden  GK 


SUPPLEMENT 


9 


The  Lizard,  England  OLD 
Liverpool,  England  GLV 
Grand  Marians,  Minn.  GM 
S.  S.  Asuncion  GM 

S.  S.  Pilgrim  GM 

Malin  Head,  Ireland  GMH 
S.  S.  Atlas  GN 

North  Foreland,  England 

GNF 

Niton,  England  GNI 

Chicago,  111.    (Congress 

Hotel)  GO 

Standard  Oil  barge  95  GP 
S.S.  City  of  Pueblo  GQ 

Copenhagen,  Denmark  GRA 
Guaraliba,  Brazil  GRA 

Rosslare,  Ireland  GRL 

Grand  Rapids,  Mich.  GRM 
S.  S.  Astral  GS 

S.  S.  Senator  GS 

S.  S.  Umatilla  GU 

Guernsey,  England  GU 

Guadalajara,  Spain  GU 

Galveston,  Texas  GV 

S.  S.  Governor  GV 

Grand  Island,  La.  GW 

S.  S.  President  GW 

S.  S.  Queen  GX 

Los  Angeles,  Cal.  G2 

Holland,  Mich.  H 

Horten,  Norway  H 

Cape  Hatteras,  N.  C.  HA 
New  Orleans,  La.  (United 

Fruit  Co.)  HB 

U.  S.  Army  Artillery  harbor 

tug  Harvey  Brown        HB 

Heysham,  England         HER 

S.  S.  Arizona  HC 

Carlobago,  Austiia-Hungary 

HC 

S.  S.  Alameda  HD 

Elizabeth  City,  N.C.          HD 


Helder,  Holland  HDR 

Fiume,  Austria-Hungary  HF 
S.  S.  Mariposa  HK 

New  Orleans,  La.  HK 

Cape  d'Aguilar,  Hongkong 

Haaks  Lightship,  Holland 

HKS 

S.  S.  Jefferson  HM 

S.  S.  Hanalia  HN 

S.  S.  Chester  W.  Chapin  HN 
S.  S.  Missouri  HN 

Hunstanton,  England  HNU 
S.  S.  Corwin  HO 

S.  S.  Chicago  HO 

Hoek  van  Holland          HOK 
Trinidad  (High  Post)         HP 
Mackinac  Island,  Mich.     HQ 
Horns  Reef  lightship,  Den- 
mark 

Cabo  Haro,  Mexico  HR 

Tug  Savage  HS 

S.  S.  Londonderry  HSM 

Nak  Nek,  Alaska  HT 

Kahuku,  Oahu,  Hawaiian  Is- 
lands HU 
Havana,  Cuba  (Vedado)  HV 
S.  S.  Grant  HV 
S.  S.  Mackinaw  HW 
Cuban  Revenue  Cutter 

Hatuey  HY 

Ludington,  Mich.  HX 

S.  S.  Humboldt  HX 

Amesbury,  Mass  HY 

S.  S.  Plymouth  HY 

Zengg,  Austria-Hungary  HZ 
S.  S.  Rose  City  H2 

Brest,  France  (arsenal)  IBF 
Ilha  das  Cobras,  Brazil  ICL 
Inistrahull,  Ireland  IH 

S.  S.  Illinois  IN 

Toulon,  France  ITF 


10        WIRELESS   OPERATORS'   POCKET  BOOK 


S.  S.  Imparatul  Traian  ITR 
Port  Vendres,  France  IVF 
S.  S.  City  of  Racine  JC 

Kingston,  Jamaica  JCA 

Chosi,  Japan  JCS 

S.  S.  North  Land  JD 

Jersey,  England  JE 

S.  S.  Horato  Hall  JH 

S.  S.  Manhattan  JM 

Otchishi,  Japan  JO  I 

Ose  Saki,  Japan  JOS 

S.  S.  North  Star  JS 

Shiomizaki,  Japan  JSM 

Tsunoshima,  Japan  JTS 

S.  S.  James  Whalen  JW 

Jacksonville,  Fla.  JX 

S.  S.  Antilles  KA 

Puako,  Hawaiian  Islands  KA 
Angaur,  Caroline  Islands 

KAN 

Spokane,  Wash.  -  KB 
Bremerhaven,  Lloyd  Hall, 

Germany  KBH 

Arkona,  Germany  KAR 

Bwlk,  Germany  KBK 

Borkum,  Germany  KBM 
Brunsbuttelkoog,  Germany 

KBR 

S.  S.  Christopher  Colum- 
bus KC 
Cuxhaven,  Germany  KCX 
S.  S.  Comus  KD 
St.  Helens.  Oreg,  KE 
S.  S.  King  Harold  KGH 
Helgoland,  Germany  KHG 
Yap,  Caroline  Islands  KJA 
S.  S.  Momus  KM 
Marienleuchte,  Germany 

KMR 

Erie,  Pa.  KN 

Norddeich,  Germany      KND 


Pachena  Point,  British 

Columbia  KPD 

S.  S.  Creole  KR 

S.  S.  Santa  Cruz  KS 

Constanca,  Roumania  KST 
The  Dalles,  Oreg.  KT 

Tsingtau,  China  KTS 

Signalberg,  Germany  KTS 
Walla  Walla,  Wash.  KU 
Key  West,  Fla.  KW 

S.  S.  Kentucky  KY 

Lahaina,  Maui,  Hawaiian  Is- 
lands   "  LH 
Machrihanish  Bay,  Scot- 
land                          LK(D) 
Cullercoats,  England        LNS 
S.  S.  Lady  Laurier  LR 
Castelneuvo,  Austria- 
Hungary                        LRC 
Pola,  Austria-Hungary   LRP 
Sebenico,  Austria-Hungary 

LRS 

Loch  Boisdale,  Scotland  LSG 
Lussin,  Austria-Hungary  LU 
Havana,  Cuba.  (Morro 

Castle)  M 

Messina,  Italy  M 

S.  S.  Alliance  MA 

S.  S.  Maine  MA 

S.  S:Carmania  MAA' 

S.  S.  Lombardia  MAB 

S.  S.  Sicilia  MAC 

S.  S.  Duca  Degli  Abruzzi 

MAD 

S.  S.  Duca  di  Geneva  MAE 
S.  S.  Mendoza  MAF 

S.  S.  Cordova  MAG 

S.  S.  Virginia  MAH 

S.  S.  Caledonia  MAI 

S.  S.  Indiana  MAK 

S.  S.  Liguria  MAL 

S.  S.  Lusiania  MAM 


SUPPLEMENT 


11 


S.  S.  Niagara  MAN 

S.  S.  Duca  d'Aosta  MAO 
S.  S.  Sardegna  MAS 

Steam  yacht  Atalanta  MAT 
American  Tickle.  Labrador 

MAT 

Asinara,  Sardinia,  Italy  MAS 
S.  S.  Umbria  MAU 

S.  S.  Florida  MAV 

S.  S.  Alva  MAV 

S.  S.  Antony  MAY 

Mobile,  Ala.  MB 

Cable  steamer  Mackay-Ben- 
nett  MB 

S.  S.  Asturias  MBB 

S.  S.  Baltic  MBC 

Bardera,  Italy  MBD 

Cape  Bear,  Prince  Edward  Is- 
land MBE 
S.  S.  Araguay                  MBG 
Battle  Harbor,  Labrador 

MBH 
Belle  Isle,  Newfoundland 

MBI 
Bernal.  Argentine  Republic 

MBL 

S.  S.  Arragon  MEN 

S.  S.  Avon  MBO 

S.  S.  Ben  My  Chree  MBQ 
Bloomfield,  England  MBR 
Palm  Beach.  Fla.  MBS 

Becco  di  Vela,  Caprera, 

Italy  MBV 

S.  S.  Athenie  MBW 

Brava,  Italy  MBW 

S.  S.  Old  Colony  MC 

S.  S.  Sheboygan  MC 

S.  S.  Campania  MCA 

Chateau  Bay,  Labrador  MCB 
Cape  Cod,  Mass.  MCC 

Steam  yacht  Cassandra  MCD 
S.  S.  Cambria  MCG 


Mocangue,  Brazil  MCG 

S.  S.  California  MCI 

Point  Rich.  Nova  Scotia 

MCH 

S.  S.  Chili  MCI 

Clarke  City,  Seven  Islands, 

Canada  MCK 

Cable  ship  Colonia  MCL 
Capo  Mele,  Liguria,  Italy 

MCM 

S.  S.  Corsican  MCN 

S.  S.  Chaco  MCO 

Monte  Capuccini,  Ancona, 

Italy  MCP 

Cape  Ray,  Newfoundland 

MCR 

S.  S.  Bucaneer  MCT 

Cape  May,  N.  J.  MCY 

Cozzo  Spadaro,  Cape  Passaro, 

Sicily  MCZ 

S.  S.  Cristobal  MD 

S.  S.  Shinnecock-  MD 

S.  S.  Cedric  MDC 

S.  S.  Dominion  MDF 

S.  S.  Devonian  MDL 

S.  S.  Sardinian  MDN 

Domino  Island,  Labrador 

MDO 

Steam  yacht  Electra  ME 
S.  S.  Etruria  MEA 

S.  S.  Tarnarac  MEB 

S.  S.  Narragansett  MEG 

S.  S.  Cassandra  MED 

S.  S.  Iroquois  MEI 

Merka,  Italy  MEK 

S.  S.  Bohemian  MEL 

Melilla,  Morocco  MEL 

S.  S.  Navahoe  MEN 

S.  S.  Empress  Queen  MEQ 
S.  S.  Royal  Edward  MER 
S.  S.  Satrustegin  MES 

S.  S.  Alfonse  XII  MET 


12        WIRELESS   OPERATORS'   POCKET  BOOK 


S.  S.  Finance 
S.  S.  Lusitania 
S.  S.  Arabic 
S.  S.  Canada 
S.  S.  Finland 


MF 
MFA 
MFC 
MFC 
MFD 


S.  S.  W.  H.  Gratwick  MFD 
Fraserburgh,  Scotland  MFH 
S.  S.  Furnessia  MFI 

S.  S.  Winifredian  MFL 

S.  S.  Pretorian  MFN 

Fame  Point,  Quebec  MFP 
Fort  Spuria,  Messina,  Italy 

MFS 

Tug  Tatoosh  MG 

S.  S.  Mauretania  MGA 

Steam  yacht  Lysistrata  MGB 
S.  S.  Cymric  MGC 

S.  S.  Saturnia  MGD 

S.  S.  Germania  MGE 

S.  S.  Harvard  MGH 

Grosse  Isle,  Quebec  MGI 
S.  S.  Canadian  MGL 

S.  S.  Virginian  MGN 

Giumbo,  Italy  MGO 

S.  S.  Royal  George  MGR 
S.  S.  Yale  MGY 

S.  S.  Panama  MH 

S.  S.  Noordan  MHA 

S.  S.  New  Amsterdam  MHB 
S.  S.  Adriatic  MHC 

New  Haven,  England  MHH 
S.  S.  Cestrian  MHL 

S.  S.  Potsdam  MHM 

S.  S.  Cartheginian  MHN 

Heath  Point,  Anticosti  Island, 

Canada  MHP 

S.  S.  Rotterdam  MHR 

S.  S.  Statendam  MHS 

Camperdown,  Halifax,  Nova 

Scotia  MHX 

S.  S.  Rijndam  MHY 

S.  S.  Minnesota  MI 


S.  S.  Ivernia 
S.  S.  Laurent ic 
S.  S.  Inanda 
S.  S.  Inkosi 
S.  S.  lolanda 


MIA 
MIC 
MID 
MIK 
MIL 


S.  S.  Principesa  Mafalda  MIM 

S.  S.  Ionian  MIN 
S.  S.  Principesa  lolanda  MIO 

Itala,  Italy  MIT 

S.  S.  Suevic  MJC 

S.  S.  Haverford  MJH 

S.  S.  Merion  MJM 

S.  S.  Millinocket  MK 

Milwaukee,  Wis.  MK 

S.  S.  Olympic  MKC 

S.  S.  Kroonland  MKD 

S.  S.  Frisia  MKF 

S.  S.  Hollarfd  MKH 

S.  S.  Corinthian  MKN 

S.  S.  Makura  MKU 

S.  S.  Killarney  MKY 

S.  S.  Montcalm  ML 

S.  S.  Guadeloupe  MLA 

S.  S.  La  Bretagne  MLB 

S.  S.  Celtic  MLC 

S.  S.  Leopold  II  MLD 

S.  S.  Lake  Erie  MLE 

S.  S.  Milwaukee  MLF 

S.  S.  La  Flandre  MLF 

S.  S.  La  Gascoyne  MLG 

S.  S.  Lake  Michigan  MLH 

S.  S.  Montreal  MLI 

S.  S.  Montrose  MLJ 

S.  S.  Montezuma  MLK 

S.  S.  La  Lorraine  MLL 

S.  S.  Lake  Manitoba  MLM 

S.  S.  Lake  Champlain  MLN 

S.  S.  Mount  Royal  MLO 

S.  S.  La  Provence  MLP 

S.  S.  Mount  Temple  MLQ 

S.  S.  La  Navarre  MLR 

S.  S.  La  Savoie  MLS 


SUPPLEMENT 


13 


S.  S.  La  Touraine 

S.  S.  La  Champagne 

Lugh,  Italy 

S.  S.  Montfort 

S.  S.  Monmouth 

S.  S.  Chicago 

S.  S.  Montcalm 

S.  S.  Minnehaha 

S.  S.  Madonna 

S.  S.  Majestic 

S.  S.  Ma'lwa 

S.  S.  Mantua 

S.  S.  Morea 

S.  S.  Egypt 

S.  S.  Moldavia 

S.  S.  Marie  Henriette 

S.  S.  Charles  Roux 

S.  S.  Mongolia 

S.  S.  Minnetonka 

S.  S.  Macedonia 

S.  S.  Mooltan 

S.  S.  Minneapolis 


MLT 
MLU 
MLU 
MLW 
MLX 
MLY 
MLZ 
MMA 
MMB 
MMC 
MMD 
MME 
MMF 
MMG 
MMH 
MMH 
MMI 
MMJ 
MMK 
MML 
MMM 
MMN 


Punta  del  Este,  Uragua 


S.  S.  Persia 
S.  S.  Marmora 


MMO 
MMQ 
MMR 

San  Guilano  di  Trapani, 

Italy  MMS 

S.  S.  Salsette  MMT 

S.  S.  China  MMU 

S.  S.  Perou  MMV 

S.  S.  Mesaba  MMV 

S.  S.  Minnewaska  MMW 

S.  S.  India  MMY 

S.  S.  Arabia  MMZ 

Tug  Lome  MN 

S.  S.  Manitou  MN 

S.  S.  Pannonia  MNA 

S.  S.  Romanic  MNC 

North  Sydney.  Canada  MND 
S.  S.  Menominee  MNE 

S.  S.  Grotius  MNG 


S.  S.  New  York  MHK 

S.  S.  Manitou  MNM 

S.  S.  Numidian  MNN 

S.  S.  Oranje  MNO 

S.  S.  Prinses  Juliana  MNP 
S.  S.  Marquette  MNQ 

S.  S.  Rembrandt  MNR 

Indian  Harbor,  Labrador 

MNR 

S.  S.  Konig  Wilhelm  III  MNT 
S.  S.  Vondel  MNV 

S.  S.  Konig  Wilhelm  I  MNW 
S.  S.  Ancona  •  MOA 

S.  S.  Bologna  MOB 

S.  S.  Oceanic  MOC 

S.  S.  Otrato  MOO 

S.  S.  Sienna  MOE 

S.  S.  Columbia  MOI 

S.  S.  Mongolian  MON 

S.  S.  Ravenna  MOR 

S.  S.  Toscana  MOS 

S.  S.  Taormina  MOT 

S.  S.  Verona  MOV 

S.  S.  Carpathia  MPA 

S.  S.  Empress  of  Britain  MPB 
S.  S.  Canopic  MFC 

S.  S.  Princess  Clementine 

MFC 

Poldhu,  England  MPD 

S.  S.  Lapland  MPD 

S.  S.  Princess  Elizabeth  MPE 
S.  S.  Empress  of  China  MPG 
S.  S.  Philadelphia  MPH 

S.  S.  Princess  Henriette  MPH 
S.  S.  Empress  of  India  MPI 
S.  S.  Empress  of  Japan  MPJ 
S.  S.  Princess  Josephine  MPL 
S.  S.  Empress  of  Ireland  MPL 
Palmaria,  Italjt  MPM 

Capo  Sperone,  Sardinia, 

Italy  MPN 

Point  Amour,  Labrador  MPR 


14        WIRELESS  OPERATORS'   POCKETBOOK 


Ponza  Island,  Italy  MPS 
S.  S.  Patris  MPT 

S.  S.  Balmoral  Castle  MPW 
S.  S.  Persic  MQC 

S.  S.  Bunker  Hill  MR 

S.  S.  Caronia  MRA 

S.  S.  Roma  MRB 

S.  S.Cretic  MRC- 

S.  S.  Sindoro  •    MRD 

S.  S.  Regina  Elena  MRE 
S.  S.  Sannio  MRF 

S.  S.  Regina  d'ltalia  MRG 
S.  S.  Campania  MRH 

S.  S.  Re  d'ltalia  MRI 

S.  S.  Ophir  MRJ 

S.  S.  Kawi  MRK 

Monte  Mario,  Rome,  Italy 

MRM 

S.  S.  Grampian  MRN 

S.  S.  Re  Vittorip  MRO 

S.  S.  Principe  di  Piedmonte 

MRP 

S.  S.  Soentuer  MRQ 

S.  S.  Rindjani  MRM 

S.  S.  Tomasodi  Savoia  MRS 
Three  Rivers,  Canada  MRS 
Father  Point,  Quebec  MRT 
S.  S.  Principe  Umberto  MRU 
S.  S.  Principe  di'  Udine  MRV 
S.  S.  Willis  MRW 

S.  S.  Tambora  MRY 

S.  S.  Lazio  MRZ 

S.  S.  Ancon  MS 

S.  S.  Massachusetts  MS 

S.  S.  Saxonia  MSA 

Cape  Sable,  Nova  Scotia 

MSB 

Siasconsett,  Mass.  MSC 

Sable  Island,  Nova  Scotia 

MSB 

Sea  Gate,  N.  Y  .  MSE 

S.  S  San  Giovanni  MSF 


S.  S.  San  Georgio  .  MSH 

St.  John,   Pattridge  Island, 

New  Brunswick  MSJ 

Sagaponack,  N.  Y.  MSK 
Santa  Maria  di  Leuca, 

Italy  MSL 

S.  S.  St.  Louis  MSL 

S.  S.  San  Guiseppi  MSN 

S.  S.  Hesperian  MSN 

S.  S.  San  Gugliemo  MSO 
S.  S.  St.  Paul  MSP 

Wellfleet,  Cape  Cod,  Mass. 

MSW 

S.  S.  Minto  MT 

S.  S.  Ultonia  MTA 

S.  S.  Teutonic  MTC 

Cross  Sand  lightship, 

England  MTD 

East  Goodwin  lightship  Eng- 
land MTE 
Gull  lightship,  England  MTG 
S.  S.  Themistocles  MTH 
S.  S.  Athinai  MTI 
Steam  yacht  Florence  MTK 
Sunk  lightship, "England 

MTK 

Montreal,  Quebec  MTL 

S.  S.  Tunisian  MTN 

Torre  Pilot!  di  Malamocco, 

Italy  MTP 

S.  S.  Trotona  MTR 

South  Goodwin  lightship, 

England  MTS- 

Tongue  lightship.  England 

MTT 

Murdock,  Chelsea,  Mass.  MU 
Musil,  Austria-Hungary  MU 
S.  S.  Umbria  MUA 

S.  S.  Titanic  MUG 

S.  S.  Francesca  MUF 

S.  S.  Argentina  MUG 

S.  S.  Alice  MUL 


SUPPLEMENT 


S.  S.  Sicilian  MUN 

S.  S.  Oceania  MUO 

S.  S.  Laura  MUR 

S.  S.  Sophia  MUS 

S.  S.  Martha  Washington 

MUW 

S.  S.  Advance  MV 

S.  S.  New  Haven  MV 

S.  S.  Argentina  MVA 

S.  S.  Bresilia  MVB 

S.  S.  Italia  MVC 

S.  S.  Vaderland  MVD 

Montevideo,  Uruguay  MVD 
S.  S.  Europa  MVE 

S.  S.  Savoia  MVF 

Venison  Island,  Labrador 

MVI 
Steam  yacht  The  Viking 

S.  S.  Victorian  MVN 

S.  S.  Oceania  MVO 

S.  S.  Viking  MVQ 

S.  S.  Nord  America  MVR 
S.  S.  America  .  MVS 

Viesti,  Mount  Gargano, 

Italy  MVT 

S.  S.  Venezia  MVZ 

S.  S.  Maurence  MW 

Manitowoc,  Wis.  MW 

Wilhelmshaven,  Germany 

MW 

Vladivostok,  Siberia  MW 
S.  S.  Aaro  MWA 

S.  S.  Runic  MWC 

S.  S.  Ionic  MWI 

S.  S.  Athenic  MWN 

S.  S.  Oslo  MWO 

Whittle  Rocks,  Quebec  MWR 
Withernsea,  England  MWS 
S.  S.  Corinthic  MWT 

S.  S.  Colon  MX 

S.  S.  Medic  MXC 


S.  S.  Afric  MYC 

Mazatlan,  Mexico  MZ 

S.  S.  Zealandia  MZA 

S.  S.  Bornu  MZB 

S.  S.  Megantic  MZC 

S.  S.  Zeeland  MZD 

S.  S.  Florizal  MZL 

S.  S.  Parisian  MZN 

S.  S.  Rosalind  MZR 

Venice,  Italty  (Arsenal) 

MZV 

Gjedser  Reef  lightship,  Den- 
mark N 
Nauen,  Germany               NA 
Cape  Elizabeth,  Me.  (naval 

station)  NAB 

Portsmouth,  N.  H.,  (navy 

yard)  NAC 

Boston,  Mass,  (navy-yard) 

NAD 
Cape  Cod,  Highland  Light, 

Mass,  (naval  station)  NAE 
Newport,  R.  I.  (naval 

station)  NAF 

Fire  Island,  N.  Y.  (naval 

station)  NAG 

Brooklyn,  N.  Y.  (navy- 
yard)  NAH 
Philadelphia,  Pa.  (navy- 
yard)  NAI 
Cape  Henlopen,  Lewes,  DeL 
(naval  station)             NAJ 
Annapolis,  Md.  ((Naval 

Academy)  NAK 

Washington,  D.  C.  (navy- 
yard)  NAL 
Norfolk,  Va.  (navy-yard) 

NAM 

Pivers  Island,  Beaufort,  N.C. 
(naval  station)  NAN 

Charleston,  S.  C.  (navy- 
yard)  NAO 


16        WIRELESS   OPERATORS'   POCKET  BOOK 


St.  Augustine    Fla.  (naval 

statiqn)  NAP 

Jupiter  Inlet,  Neptune,  Fla. 

(naval  station)  NAQ 

Key  West,  Fla.  (naval 

station)  NAR 

Pensacola,  Fla.  (navy- 
yard)  '  NAS 
New  Orleans,  La.  (naval 

station)  NAT 

San  Juan,  P.  R.  (naval 

station)  NAU 

Culebra,  W.I.  (naval 

station)  NAV 

Guantanamo,  Cuba  (U.  S. 

naval  station)  NAW 

Colon,  Isthmian  Canal  Zone 

(naval  station)  NAX 

Porto  Bello,  Isthmian  Canal 

Zone  (naval  station)  NAY 
U.  S.  S.  Ajax  NBH 

U.  S.  S.  Alabama  NBI 

U.  S.  S.  Albany  NBJ 

U.  S.  S.  Alexander  NBM 
U.  S.  S.  Arethusa  NBU 

U.  S.  S.  Bailey  NCF 

U.  S.  S.  Bainbridge  NCG 
U.  S.  S.  Baltimore  NCH 

U.  S.  S.  Barry  NCK 

U.  S.  S.  Biddle  NCM 

U.  S  S.  Birmingham  NCN 
U.  S.  S.  Brutus  NCT 

U.  S.  S.  Buffalo  NCU 

U.  S.  S.  Burrows  NCV 

U.  S.  S.  Caesar  NCY 

U.  S.  S.  California  NCZ 

S.  S.  Northland  ND 

U.  S.  S.  Castine  NBA 

U.  S.  S.  Celtic  NDB 

U.  S.  S.  Charleston  NDC 
U.  S.  S.  Chattanooga  NDE 
U.  S.  S.  Chauncey  NDF 


U.  S.  S.  Chester  NDG 

U.  S.  S.  Chicago  NDI 

U.  S.  S.  Cincinnati  NDL 

U.  S.  S.  Cleveland  NDM 

U.  S.  S.  Colorado  NDN 

U.  S.  S.  Connecticut  NDQ 

U.  S.  S.  Culgoa  NDU 

U.  S.  S.  Cyclops  NDY 
S.  S.  Nushagak  NE 

U.  S.  S.  Dale  NEH 

U.  S.  S.  Decatur  NEJ 

U.  S.  S.  Delaware  NEK 

U.  S.  S.  Denver  NEM 

U.  S.  S.  Des  Moines  NEN 

U.  S.  S.  Dixie  NEP 

U.  S.  S.  Dolphin  NEQ 
U.  S.  S.  Don  Juan  de  Austria 

(Michigan  Naval  Militia 

NER 

U.  S.  S.  Drayton  NET 

U.  S.  S.  Dubuque  NEU 

U.  S.  S.  Eagle  NFC 

U.  S.  S.  Farragut  NFP 

U.  S.  S.  Flusser  NFS 

U.  S.  S.  Galveston  NGD 

U.  S.  S.  Georgia  NGF 

U.  S.  S.  Glacier  NGH 

U.  S.  S.  Goldsborough  NGJ 
U.  S.  S.  Gopher  (Minnesota 

Naval  Militia)  NGK 

U.  S.  S.  Hannibal  NGU 

U.  S.  S.  Hartford  NGV 

U.  S.  S.  Hector  NGX 

U.  S.  S.  Helena  NGY 
S.  S.  Wilhelmina  NH 

U.  S.  S.  Hopkins  NHC 

U.  S.  S.  Hull  NHE 

U.  S.  S.  Idaho  NHN 

U.  S.  S.  Illinois  NHO 

U.  S.  S.  Indiana  NHQ 

U.  S.  S.  Iowa  NHT 

U.  S.  S.  Isis  NHU 


SUPPLEMENT 


17 


S.  S.  Klamath  NI 
U.  S.  S.  Jupiter  NIE 
U.  S.  S.  Justin  NIF 
U.  S.  S.  Kansas  NIO 
U.  S.  S.  Kearsarge  NIP 
U.  S.  S.  Kentucky  NIQ 
U.  S.  S.  Lamson  NIW 
U.  S.  S:  Lawrence  NIY 
U.  S.  S.  Lebanon  NIZ 
U.  S.  S.  Leonidas  NJA 
U.  S.  S.  Louisiana  NJB 
U'  S.  S.  Macdonough  NJH 
U.  S.  S.  Machias  NJI 
U.  S.  S.  Maine  NJL 
U.  S.  S.  Marietta  NJQ 
U.  S.  S.  Mars  NJR 
U.  S.  S.  Maryland  NJS 
U.  S.  S.  Massachusetts  NJT 
U.  S.  S.  Mayrant  NJU 
U.  S.  S.  Mayflower  NJV 
U.  S.  S.  McCall  NJW 
U.  S:  S.  Michigan  NJZ 
S.  S.  Pequonock  NK 
U.  S.  S.  Milwaukee  NKA 
U.  S.  S.  Minnesota  NKD 
U.  S.  S.  Mississippi  NKE 
U.  S.  S.  Missouri  NKF 
U.  S.  S.  Montana  NKM 
U.  S.  S.  Monterey  NKN 
U.  S.  S.  Montgomery  NKO 
U.  S.  S.  Nanshan  NKV 
Nantucket  Shoals  light- 
ship NLA 
Diamond  Shoals  light- 
ship NLB 
Frying  Pan  Shoals  light- 
ship NLC 
U.  S.  S.  Nebraska  NMA 
U.  S.  S.  Nero  NMB 
U.  S.  S.  New  Hampshire 

NME 

U.  S.  S.  New  Jersey  NMF 


U.  S.  S.  New  Orleans  NMG 
New  York  nautical  school 

ship  Newport  NMH 

U.  S.  S.  New  York  NMI 

U.  S.  S.  North  Carolina  NMN 
U.  S.  S.  North  Dakota  NMO 
U.  S.  S.  Ohio  NMW 

U.  S.  S.  Olympia  NMX 

Nonendamm,  Germany  NO 
U.  S.  S.  Paducah  NOG 

U.  S.  S.  Panther  NOJ 

U.  S.  S.  Patapsco  NOL 

U.  S.  S.  Patuxent  NOM 

U.  S.  S.  Paulding  NON 

U.  S.  S.  Paul  Jones  NOP 
U.  S.  S.  Pennsylvania  NOT 
U.  S.  S.  Perkins  NOX 

U.  S.  S.  Perry  NOY 

Cordova,  Alaska  (naval 

station)  NPA 

Sitka,  Alaska  (naval 

station)  NPB 

Bremerton,  Wash,  (navy- 
yard)  NPC 
Tatoosh  Island,  Wash,  (naval 
station)                         NPD 
North  Head,  Wash,  (naval 

station)  NPE 

Cape  Blanco,  Oreg.  (naval 

station)  NPF 

Table  Bluff,  Cal.  (naval 

station)  NPG 

North  Post,  Trinidad      NPG 
Mare  Island,  Cal.  (navy- 
yard)  NPH 
Farallon  Islands,  Cal.  (naval 
station)  NPI 
Yerba  Buena  Island,  Cal. 

(naval  station)  NPJ 

Point  Arguello,  Cal.  (naval 
station)  NPK 


18        WIRELESS  OPERATORS'   POCKET  BOOK 


Point  Loma,  Cal.  (naval 

station)  NPL 

Honolulu,  Hawaii  (naval  sta- 
tion) NPM 
Guam.  Marianas  (naval  sta- 
tion) NPN 
Cavite,  P.  I.  (naval  station) 
NPO 

Nieuport,  Belgium  ™^ 

S.  S.  HoUand 
U.  S.  S.  Pompey 
U.  S.  S.  Prairie 
U.  S.  S.  Preble 
U,  S.  S.  Preston 
U.  S.  S.  Princeton 
U.  S.  S.  Prometheus 
U.  S.  S.  Rainbow  NRA 

U.  S.  S.  Raleigh  NRB 

Massachusetts  nautical 

school  ship  Ranger      NRG 
U.  S.  S.  Reid  NRE 

U.  S.  S.  Rhode  Island  NRI 
U.  S.  S.  Decatur  NRJ 

U.  S.  S.  Roe  NRM 

U.  S.  S.  Salem  NRZ 

.S.  S.  New  Hampshire  NS 
U.  S.  S.  Saturn  NSF 

U.  S.  S.  Scorpion  NSG 

U.  S.  S.  Smith  NSQ 

U.  S.  S.  Solace  NST 

U.  S.  S.  South  Carolina  NSW 
U.  S.  S.  South  Dakota  .  NSX 
U.  S.  S.  Sterling  NTA 

IT.  S.  S.  Sterrett  NTB 

U.  S.  S.  Stewart  NTC 

U.  S.  S.  St.  Louis  NTF 

U.  S.  S.  Stringham  NTI 

U.  S.  S.  Supply  NTK 

S.  S.  J.  S.  Chanslor  NU 

U.  S.  S.  Tacoma  NUA 

U.  S.  S.  Tennessee  NUG 

U.  S.  S.  Terry  NUI 


U.  S.  S.  Tonopah  NUN 

U.  S.  S.  Truxtun  NUS 

S.  S.  Charles  S.  Nelson  NV 
U.  S.  S.  Vermont  NVK 

U.  S.  S.  Vestal  NVL 

U.  S.  S.  Vicksburg  NVN 
U.  S,  S.  Virginia  NVR 

U.  S.  S.  Vulcan  NVT 

S.  S.  Northwest  NW 

Nawiliwili,  Kauai,  Hawaiian 
Islands  NW 

U.  S.  S.  Warrington  NWD 
U.  S.  S.  Washington  NWE 
U.  S.  S.  West  Virginia  NWG 
U.  S.  S.  Wheeling  NWH 
U.  S.  S.  Whipple  NWI 

U.  S.  S.  Wilmington  NWK 
U.  S.  S.  Wisconsin  NWM 
U.  S.  S.  Worden  NWP 

U.  S.  S.  Yankton  NXB 

U.  S.  S.  Yorktown  NXD 
New  York  ,N.  Y.  (42  Broad- 
way) NY 
Tug  Fearless  N2 
S.  S.  Hamilton  OA 
S.  S.  Atlanta  OAA 
S.  S  Columbia  OAC 
S.  S.  Sophia  Hohenberg  OAH 
S.  S.  Princess  Anne  OB 
S.  S.  Jamestown  OC 
S.  S.  Jefferson  OD 
New  York,  N.  Y.  (Herald 
ship  news  office,  The 
Battery)  OHX 
S.  S.  KayoMaru  OKY 
Pernambuco,  Brazil  OL 
S.  S.  Monroe  OM 
U.  S.  Artillery  harbor  tug 

General  Randall  OR 

S.  S.  Olivette  OV 

S.  S.  Mascotte  OW 

Berlin,  Germany  OW 


SUPPLEMENT 


19 


Oxford,  England  OX 

S.  S.  Miami  OZ 

New  York,  N.  Y.  (Hotel 

Plaza)  P 

Isle  of  Pines,  Cuba  P 

Seattle,  Wash.    (University 
grounds)  PA 

S.  S.  Prince  Albert  PA 

Ketchikan,  Alaska  PB 

Pemba  Island,  Zanzibar    PB 
Astoria,  Oreg.  PC 

Tampa,  Fla.  PD 

Friday  Harbor,  Wash.       PD 
Port  Said,  Egypt  PD 

Providence,  R.  I.  PF 

Aberdeen,  Wash.  PF 

Westport,  Wash.  PG 

Payo  Obispo,  Mexico         PG 
Point  Grey,  British  Colum- 
bia PGD 
San  Francisco,  Cal  PH 
Avalon,  Catalina  Island. 

Cal.  PI 

Fort  Frank,  P.  I.  PI  A 

Fort  Drumm,  P.  I.  PIB 

Fort  Wint,  P.  I.  PIC 

Fort  William  McKinley, 

P.  I.  PID 

Point  Judith,  R.  I.  PJ 

Los  Angeles,  Cal.   (Boyle 

Heights)  PJ 

San  Diego,  Cal.  PK* 

Porthcuno,  Cornwall  Eng- 
land PK 
Port  Tewfik,  Egypt            PK 
Peking,  China  (Italian  em- 
bassy) PK 
Eureka,  Cal.  PM 
Bahia  Blanca,  Argentine  Re- 
public PM 
Pere  Marquette  car  ferry 
No.  5                             PM5 


Alpena,  Mich.  PN 

Katalla,  Alaska  PN 

Manila,  P.  I.  PN 

Ponta  Negra,  Brazil        PNA 
Cordova,  Alaska  PO . 

Kronstadt  (Fort  Menschi- 

koff),  Russia  PPZ 

Monterey,  Cal.  PQ 

S.  S.  City  of  Chicago  PQ 

Parkeston  Quay,  England 

PQL 
North  Vancouver,  British 

Columbia  PR 

Prince  Rupert,  British  Co- 
lumbia PRD 
San  Francisco,  Cal.  (Presidio) 
PS 

Port  of  Spain,  Trinidad      PS 
Port  Bragg,  Cal.  PT 

St.  Petersburg,  Russia     PTB 
Bellingham,  Wash.  PU 

S.  S.  Mobilla  PU 

S.  S.  Providence  PV 

Victoria,  British  Columbia 

PW 

Los  Angeles,  Cal.  (Exam- 
iner) PX 
Olympia.  Wash,  PY 
S.  S.  Enterprise  PI 
S.  S.  Hilonian  P2 
S.  S.  Portland  P3 
S.  S.  Col.  E.  L.  Drake  P4 
Standard  Oil  barge  3  P5 
S  S,  Buckman  P7 
S.  S.  Watson  P8 
S.  S.  Bertha  P9 
Quebec  Q 
Bluefields,  Nicaragua  Q 
Alderney,  England  QDH 
Washington,  D.  C  (Elliott 

Woods)  QK 

Antwerp,  Belgium  QR 


20        WIRELESS   OPERATORS'   POCKET  BOOK 


Bermuda  QWC 

Reggio,  Italy  R 

S.  S.  Algerie  RAG 

S.  S.  Governor  Cobb          RB 

Lightship  Recalada,  La  Plata 
River,  Argentine  Re- 
public RC 

II.  S.  revenue  cutter  Algon- 
quin RCA 

U.  S.  revenue  cutter  Bear 

RGB 

U.  S.  revenue  cutter  Andros- 
coggin  ROD 

U.  S.  revenue  cutter  Seneca 
RCE 

U.  S.  revenue  cutter  Sno- 
homish  RCF 

U.  S.  revenue  cutter  Gres- 
ham  RCG 

U.  S.  revenue  cutter  McCul- 
lough  RCH 

U.  S.  revenue  cutter  Itasca 
RCI 

U.  S.  revenue  cutter  Wood- 
bury  RCJ 

U.  S.  revenue  cutter  Tahoma 
RCK 

U.  S.  revenue  cutter  Tusca- 
rora  RCL 

U.  S.  revenue  cutter  Mo- 
hawk ROM 

U.  S.  revenue  cutter  Mann- 
ing RCN 

U.  S.  revenue  cutter  Onon- 
daga  RCO 

U.  S.  revenue  cutter  Apache 
RCP 

U.  S.  revenue  cutter  Perry 

RCQ 

U.  S.  revenue  cutter  Rush 

RCR 


U.  S.  revenue  cutter  Semi- 

nole  RCS 

U.  S.  revenue  cutter  Thetis 

RCT 

U.  S.  revenue  cutter  Acush- 

net  RCU 

U.  S.  revenue  cutter  Win- 

dom  RCW 

U.  S.  revenue  cutter  Yama- 

craw  RCY 

S.  S.  La  Rapide  RD 

S.  S.  France  RFR 

S.  S.  Formosa  RFS 

New  Haven,  England  RHN 

S.  S.  Ile-de-France  RIF 

S.  S.  Russie  RIO 

S.  S.  Italic  RIT 

Tug  Relief  RJ 

Rio  de  Janeiro,  Brazil  RJ 

Rijo,  Brazil  RJI 

Corkbeg,  England  RJF 

Santa  Rosalia,  Mexico  RH 

S.  S.  Plata  RLA 

S.  S.  Puritan  RN 

S.  S.  Calvin  Austin  RN 

S.  S.  Atrato  RNA 

Magdalena  RND 

S.  S.  Nile  RNJ 

S.  S.  Clyde  RNK 

S.  S.  Thames  RNM 

S.  S.  Orinoco  RNO 

S.  S.  Ortona  RNQ 

S.  S.  Trent  RNR 

S.  S.  Tagus  RNS 

S.  S.  Orotava  RNV 

S.  S.  Oruba  RNU 

S.  S.  Berbice  RNX 

S.  S.  Premier  RP 

S.  S.  Pampa  RPP 

S.  S.  Parana  RPR 

S.  S.  I.  J.  Merritt  RQ 

S.  S.  Marquette  RQ 


SUPPLEMENT 


21 


Dover,  England  RQW 

Rixhoft,  Germany  RRX 
S.  S.  Rescue  RS 

Pinar  del  Rio,  Cuba  RS 

Rost,  Norway  RST 

Port  Arthur,  Tex.  RU 

S.  S.  Governor  Dingley  RV 
IT.  S.  Artillery  Harbor  Tug 

Captain  Rowell  RW 

Mexican  cable  ship  Relay  RX 
S.  S.  Yale  RY 

Raza,  Brazil  RZA 

Cambridge,  Mass.  S 

8.  S.  Salvor  SAL 

S.  S.  Satellite  SAT 

S.  S.  Prinz  August  Wil- 

helm  SB 

S.  S.  Birma  SBA 

S.  S.  Indiana  SC 

S.  S.  Tasco  SC 

Bari,  Italy  SC 

S.  S.  J.  F.  Tietgen  SCF 

Scheveningen,  Holland  SCH 
Felixstowe,  England  -SCQ 
S.  S.  Estonia  .  SEA 

n  Franciso,  Cal.  SF 

S.  S.  Prinz  Eitel  Frederich  SF 
S.  S.  Prinz  Sigismund  SG 
Sault  Ste.  Marie,  Mich.  SH 
S.  S.  Oceana  SK 

Cape  Lazo,  B.  C.  SKD 

Skegness,  England  SKE 

San  Jose  del  Cabo,  Mexico  SJ 
S.  S.  Litunia  SLA 

S.  S.  Sierra  SM 

Ponta  Delgado,  San  Miguel, 

Azores  SMG 

Windmill  Hill,  Gibraltar  SMP 
Charleston,  S.  C.  (Hampton 

Park)  SN 

Santiago  de  Cuba,  Cuba  SN 
Barge  Shenango  SNA 


S.  S.  Wm.  P.  Porter  SND 
S.  S.  Wilpen  SNW 

S.S.King  Oscar  1 1  SOR 
Sorvaagen,  Norway  SOT 
S.  S.  Prinz  Joachim  SP 

S.  S.  Russia  SRN 

S.  S.  Puritan  SQ 

S.  S.  Stanley  ST 

Santa  Maria,  Azores  STM 
Savannah,  Ga.  SV 

Southwest  Pass,  La.  SW 
Seattle,  Wash.  S2 

Cherbourg,  France  TCF 

S.  S.  Chito  Maru  TOY 

Dunkerque,  France  TDF 
Tobermory  Island,  Scot- 
land THM 
S.  S.  Hong  Kong  Maru  THN 
Triangle  Island,  British  Co- 
lumbia TLD 
Lorient,  France  TLF 
Port  Patrick,  England  TLK 
S.  S.  America  Maru  TMC 
Tjomo,  Norway  TMO 
Rame  Head,  England  TMP 
S.  S.  Tennessee  TN 
Tienstin,  China  TN 
S.  S.  Nippon  Maru  TNP 
Oran,  Algeria  TOF 
Brest,  France  TQF 
S.  S.  Rosina  TR 
Rochefort,  France  TRF 
S.  S.  Tenyo  Maru  TTY 
Tempelhofer,  Germany  TU 
Kiel,  Germany  (torpedo 

station)  TVK 

Scilly  Islands,  England  TVP 
Tangier,  Morocco  TW 

Portland,  England          TWQ 
New  York,  N.  Y.,  (Ill  Broad 
way)  TWT 

S.  S.  Jos.  Vacarro  TY 


22        WIRELESS  OPERATORS'   POCKET  BOOK 


Tacoma,  Wash.  T2 

S.  S.  Ellis  UA 

S.  S.  Preston  UB 

Boulogne,  France  UBL 

S  S.  Buffalo  UBO 

8  S.  Cartago  WC 

S.  S.  Ucayali  UCL 

S.  S.  Lansing  UD 

S.  S.  Parisiana  UD 

S.  S.  Idaho  UDI 

Rama,  Nicaragua  UE 

S.  S.  Admiral  Schley  UG 

S.  S.  Galilee  UGO 

S.  S.  Heredia  UH 

S.  S.  Herman  Frasch  UHF 

S.  S.  Noruega  URG 
S.  S.  Highland  Laddie    UHL 

S.  S.  Highland  Pride  UHP 

S.  S.  Highland  Rover  UHR 
Cape  San  Antonio,  Cuba    UJ 

S.  S.  Acre  UJA 

S.  S.  Sergipe  UJB 

S.  S.  Orion  UJC 

S.  S.  Bahia  UJG 

S.  S.  Marnhao  UJH 

S.  S.  Olinda  UJI 

S.  S.  Brazil  UJK 

S.  S.  San  Salvador  UJM 

S.  S.  Goyaz  UJN 

S.  S.  Para  UJO 

S.  S.  Saturno  UJP 

S.  S.  Manaos  UJQ 

S.  S.  Jupiter  UJR 

S.  S.  Ceara  UJV 

S.  S.  Alagoas  UJY 

S.  S.  Sirio  UJZ 

S.  S.  Turralba.  UK 

S.  S.  Huallaga  ULA 

S.  S.  Santa  Maria  UM 

S.  S.  Antenas  UM 

S.S.Druid  UMD 

Ouessant,  France  UOS 


S.  S.  Prince  George  UPG 
Porquerolies  France  UPQ 
S.  S.  Prince  Rupert  UPR 
S.  S.  Santa  Rita  t'S 

Estevan  Point,  B.  C.  USD 
S.  S.  Eskimo  USK 

St.  Marie  de  la  Mer,  France 

USM 

S.  S.  St.  Vincent  USV 

S.  S.  Admiral  Dewey  CV 
S.  S.  Verdi  UVD 

S.  S.  Vasari  UVR 

S.  S.  Admiral  Farragut  UW 
S.  S.  Pectan  l"\Y 

S.  S.  San  Paulo  UWK 

S.  S.  Minas  Geraes  I  \V\ 
S.  S.  Rio  de  Janeiro  UWR 
S.S.Texas  1  \s 

S.  S.  Lurline  U2 

San  Giovanni,  Italy  V 

S.  S.  Apache  VA 

S.  S.  Arapahoe  VB 

S.  S.  Comanche  VC 

S.  S.  Villa  de  Douvres  VD 
Yacht  Vanadis  YDS 

S.  S.  Iroquois  VF 

Sheerness,  England  VFM 
S.  S.  Algonquin  VG 

S.  S.  Huron  VH 

S.  S.  Seminole  VJ 

S.  S.  Cherokee  VK 

Wyl  lightship,  Denmark  VL 
S.  S.  Mohawk  VM 

Victoria,  British  Columbia 

VSD 

Victoria,  British  Columbia  V2 
New  York,  N.  Y.  (Waldorf- 
Astoria)  WA 
S.  S.  China  WA 
S.  S.  W.  B.  Davock  WB 
S.  S.  Beaver  WB 
Wiborg,  Italy  WB 


SUPPLEMENT 


S.  S.  Morro  Castle  WC 

S.  S.  Bear  WD 

Bayonne,  NJ.  WD 

S.  S.  City  of  Lowell  WE 

S.  S.  Manchuria  WK 

Escuela  Naval,  Chile  WEN 
Playa  Ancha,  Chile  WFT 
S.  S.  Seguranca  WG 

S.  S.  Havana  WH 

S.  S.  Korea  WK 

Las  Salinas,  Chile  •  WLS 
S.  S.  Merida  WM 

S.  S.  Mongolia  WN 

Wilsons  Point,  Conn.  WN 
Eastport,  Me.  WQ 

S.  S.  City  of  Traverse  WQ 
New  London,  Conn.  WS 

S.  S.  Asia  WT 

S.  S.  Siberia  WU 

S.  S.  Vigilancia  WV 

S.  S.  Mexico  WX 

S.  S.  Monterey  WY 

Motor  yacht  Sea  Otter  WY 
S.  S.  Esperanza  WZ 

U.  S.  Artillery  harbor  tug 

Reno  X 

Port  Limon,  Costa  Rico  X 
S.  S.  Hendrick  Hudson  XA 
S.  S.  Arizona  XA 

S.  S.  City  of  Philadelphia  XA 
New  York,  N.  Y.   (66  Broad- 
way) XAS 
New  York,  N.  Y.    (Metropo- 
litan tower)                  XAV 
S.  S.  City  of  Wilmington  XB 
S.  S.  Robert  Fulton  XB 
Philadelphia,  Pa.             XBG 
Washington,  D.  C.    (Evans 

Building)  XBM 

S.  S.  Walter  Adams  XD 

S.  S.  Florida  XF 


23- 

S.  S.  Alabama  GX 

S.  S.  Virginia  XK 

S.  S.  Alaska  XK 

Duluth,  Minn.  XKA 

Houghton,  Mich.  XKD 

Sault  Ste.  Marie,  Mich.  XKG 

Cheboygan,  Mich.  XKJ 

Toledo,  Ohio  XKS 

Cleveland,  Ohio  XKW 

S.  S.  Mindora  XM 

Escanaba,  Wis.  XMB 

Milwaukee,  Wis.  XMH 

Chicago,  111.  XMJ 

Michigan  City,  Ind.  XMQ 

Ludington,  Mich.  XMV 

S.  S.  J.  L.  Lawrence  XN 

S.  S.  City  of  Norfolk  XN 

S.  S.  City  of  Baltimore  XO 

Xcalac,  Mexico  XP 

S.  S.  Louise  XQ 

S.  S.  Quick  Step  XQ 

S.  S.  Jos.  Whartori  XW 
S.  S.  S.  V.  Luckenbach      YA 

S.  S.  Paraguay  YA 

S.S.Thalia    "  YA 

S.  S.  Aki  Maru  YAK 

S.  S.  Awa  Maru  YAW 

S.  S.  Toledo  YD 

S.  S.  Inaba  Maru  YIB 

S.  S.  lyo  Maru  YIY 

S.  S.  Kaga  Maru  YKG 

S.  S.  Illinois  YN 

S.  S.  Shinano  Maru  YSN 

S.  S.  Tamba  Maru  -YTB 

S.  S.  Tango  Maru  YTG 

S.  S.  Toso  Maru  YTS 

S.  S.  Ossabow  ZB 

S.  S.  Ogeechee  ZK 

S.  S.Satilla  ZM 

S.  S.  Altamaha  --ZQ 

Zanzibar  ZR  ' 

S.  S  Ocmulgee  ZU 


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AN     ~ 


. 


No  30*5  5,  * 


HORARY  USE 


'I  23  1955 


5627 


< 


222658 


